Second harmonic generating (SHG) nanoprobes have recently emerged as versatile and durable labels suitable for in vivo imaging, circumventing many of the inherent drawbacks encountered with classical fluorescent probes. Since their nanocrystalline structure lacks a central point of symmetry, they are capable of generating second harmonic signal under intense illumination – converting two photons into one photon of half the incident wavelength – and can be detected by conventional two‐photon microscopy. Because the optical signal of SHG nanoprobes is based (...) on scattering, rather than absorption as in the case of fluorescent probes, they neither bleach nor blink, and the signal does not saturate with increasing illumination intensity. When SHG nanoprobes are used to image live tissue, the SHG signal can be detected with little background signal, and they are physiologically inert, showing excellent long‐term photostability. Because of their photophysical properties, SHG nanoprobes provide unique advantages for molecular imaging of living cells and tissues with unmatched sensitivity and temporal resolution. (shrink)

The discovery and engineering of novel fluorescent proteins (FPs) from diverse organisms is yielding fluorophores with exceptional characteristics for live‐cell imaging. In particular, the development of FPs for fluorescence (or Förster) resonance energy transfer (FRET) microscopy is providing important tools for monitoring dynamic protein interactions inside living cells. The increased interest in FRET microscopy has driven the development of many different methods to measure FRET. However, the interpretation of FRET measurements is complicated by several factors including the high fluorescence (...) background, the potential for photoconversion artifacts and the relatively low dynamic range afforded by this technique. Here, we describe the advantages and disadvantages of four methods commonly used in FRET microscopy. We then discuss the selection of FPs for the different FRET methods, identifying the most useful FP candidates for FRET microscopy. The recent success in expanding the FP color palette offers the opportunity to explore new FRET pairs. (shrink)

Fluorescence correlation spectroscopy (FCS) is a powerful technique to measure concentrations, mobilities, and interactions of fluorescent biomolecules. It can be applied to various biological systems such as simple homogeneous solutions, cells, artificial, or cellular membranes and whole organisms. Here, we introduce the basic principle of FCS, discuss its application to biological questions as well as its limitations and challenges, present an overview of novel technical developments to overcome those challenges, and conclude with speculations about the future applications of fluorescence (...) fluctuation spectroscopy. (shrink)

The recent development of single molecule detection techniques has opened new horizons for the study of individual macromolecules under physiological conditions. Conformational subpopulations, internal dynamics and activity of single biomolecules, parameters that have so far been hidden in large ensemble averages, are now being unveiled. Herein, we review a particular attractive solution‐based single molecule technique, fluorescence correlation spectroscopy (FCS). This time‐averaging fluctuation analysis which is usually performed in Confocal setups combines maximum sensitivity with high statistical confidence. FCS has proven to (...) be a very versatile and powerful tool for detection and temporal investigation of biomolecules at ultralow concentrations on surfaces, in solution, and in living cells. The introduction of dual‐color cross‐correlation and two‐photon excitation in FCS experiments is currently increasing the number of promising applications of FCS to biological research. BioEssays 24:758–764, 2002. © 2002 Wiley Periodicals, Inc. (shrink)

A cell's biochemistry is now known to be the biochemistry of molecular machines, that is, protein complexes that are assembled and dismantled in particular locations within the cell as needed. One important element in our understanding has been the ability to begin to see where proteins are in cells and what they are doing as they go about their business. Accordingly, there is now a strong impetus to discover new ways of looking at the workings of proteins in living cells. (...) Although the use of fluorescent tags to track individual proteins in cells has a long history, the availability of laser-based confocal microscopes and the imaginative exploitation of the green fluorescent protein from jellyfish have provided new tools of great diversity and utility. It is now possible to watch a protein bind its substrate or its partners in real time and with submicron resolution within a single cell. The importance of processes of self-organisation represented by protein folding on the one hand and subcellular organelles on the other are well recognised. Self-organisation at the intermediate level of multimeric protein complexes is now open to inspection. BioEssays 22:180–187, 2000. ©2000 John Wiley & Sons, Inc. (shrink)

Fluorescence microscopy is the primary tool for studying complex processes inside individual living cells. Technical advances in both molecular biology and microscopy have made it possible to image cells from many genetic and environmental backgrounds. These images contain a vast amount of information, which is often hidden behind various sources of noise, convoluted with other information and stochastic in nature. Accessing the desired biological information therefore requires new tools of computational image analysis and modeling. Here, we review some of the (...) recent advances in computational analysis of images obtained from fluorescence microscopy, focusing on bacterial systems. We emphasize techniques that are readily available to molecular and cell biologists but also point out examples where problem‐specific image analyses are necessary. Thus, image analysis is not only a toolkit to be applied to new images but also an integral part of the design and implementation of a microscopy experiment. (shrink)

Phototoxicity frequently occurs during live fluorescence microscopy, and its consequences are often underestimated. Damage to cellular macromolecules upon excitation light illumination can impair sample physiology, and even lead to sample death. In this review, we explain how phototoxicity influences live samples, and we highlight that, besides the obvious effects of phototoxicity, there are often subtler consequences of illumination that are imperceptible when only the morphology of samples is examined. Such less apparent manifestations of phototoxicity are equally problematic, and can change (...) the conclusions drawn from an experiment. Thus, limiting phototoxicity is a prerequisite for obtaining reproducible quantitative data on biological processes. We present strategies to reduce phototoxicity, e.g. limiting the illumination to the focal plane and suggest controls for phototoxicity effects. Overall, we argue that phototoxicity needs increased attention from researchers when designing experiments, and when evaluating research findings. (shrink)

Members of the family of the Green Fluorescent Protein (GFP) are the only known type of natural pigments that are essentially encoded by a single gene, since both the substrate for pigment biosynthesis and the necessary catalytic moieties are provided within a single polypeptide chain. In sharp contrast to the state of knowledge just three years ago when GFP was the only known protein of its kind, a whole family of related proteins, exhibiting striking diversity of features have now (...) been identified. This provides new possibilities for a variety of studies ranging from applied biotechnology to evolutionary ecology. BioEssays 24:953–959, 2002. © 2002 Wiley Periodicals, Inc. (shrink)

Fluorescence microscopy has provided a route to qualitatively analyze features of nuclear structures and chromatin domains with increasing resolution. However, it is becoming increasingly important to develop tools for quantitative analysis. Here, we present an automated method to quantitatively determine the enrichment of several endogenous factors, immunostained in pericentric heterochromatin domains in mouse cells. We show that this method permits an unbiased characterization of changes in the enrichment of several factors with statistical significance from a large number of nuclei. Furthermore, (...) the nuclei can be sorted according to the enrichment value of these factors. This method should prove useful to monitor events related to changes in the amount, rather than the presence or absence, of any factor. By adapting a few parameters, it could be extended to other nuclear structures and the benefit of using available software will permit its use in many biological labs. (shrink)

— We prescnt here a comparative study on the decay of chlorophyll a fluorescence yield in thylakoid membranes and photosystem 11 ‐enriched samples, measured with multifrequency cross‐correlation phase fluorometry. These measurements confirm the general conclusions of Van Mieghem ef al., obtained with a flash method, on the effects of reduction of the primary quinone acceptor on ChI a fluorescence yield of PSI. Different states of the reaction centers of PSII were produced by: pretreatment with sodium dithionite and mcthyl viologen followed (...) by laser illumination: the doubly reduced QA centers: with laser illumination or pretreatment with diuron: QA‐ centers; and the addition of micromolar concentration of dichlorobenzoquinonc : oxidized QA centers. The data were analyzed with Lorentzian distribution as well as with multiexponential fluorescence decay functions. The analysis with Lorcntzian distribution function showed that upon formation of QA. the major lifetime distribution peak shifted to longer lifetimes: from 0.25 ns to 1.66 ns and from 0.24 ns to 1.31 ns. However, when QAHZ was formed, the lifetime distribution peaks shifted back to shorter lifetimes both in thylakoids and PSIl membranes. Multiexponential analysis showed three lifetime components: fast, middle and slow. When QA was formed in PS11 centers, the amplitude of the fast Component decreased, but both thc amplitude and the lifetime of the middle component increased severalfold. However, when QA was doubly reduccd, the amplitude of the fast component increased and the amplitude of the middle component decreased: in addition, the lifetime of the slow component increased. All of the above results are consistent with the conclusions that PS11 charge separation is decreased when QA is formed and increased when doubly reduced QA is formed. Copyright © 1993, Wiley Blackwell. All rights reserved. (shrink)

This study renews the classical concept of subliminal perception by investigating the impact of subliminal flicker from fluorescent lighting on affect and cognitive performance. It was predicted that low compared to high frequency lighting would evoke larger changes in affective states and also impair cognitive performance. Subjects reported high rather than low frequency lighting to be more pleasant, which, in turn, enhanced their problem solving performance. This suggests that sensory processing can take place outside of conscious awareness resulting in (...) conscious emotional consequences; indicating a role of affect in subliminal/implicit perception, and that positive affect may facilitate cognitive task performance. (shrink)

Selected aneuploidies can be rapidly diagnosed by the analysis of fluorescent polymerase chain reaction (PCR) products of chromosome‐specific and highly polymorphic small tandem repeats (STRs). The quantitative STR patterns obtained from samples of normal individuals are markedly different from those seen when patients with aneuploidies involving chromosome X, or trisomies of chromosomes 21 and 18, are tested. For example, while samples from normal subjects – tested with a chromosome 21‐derived STR (D21S11) – show two fluorescent PCR peaks with (...) similar activities in a 1:1 ratio, the analysis of samples from patients with trisomy 21 reveals the presence of either three peaks (ratio 1:1:1), or two peaks with a ratio of 2:1. The use of an internal non‐polymorphic marker allows identification of trisomic samples with three copies of the same allele. This rapid approach (24 hours) is particularly valuable when applied to prenatal diagnosis of chromosomal abnormalities since it reduces the time of anxiety of the parents waiting for the results of the conventional cytogenetic tests, which require several weeks. (shrink)

Recently developed super‐resolution microscopy techniques are changing our understanding of lipid rafts and membrane organisation in general. The lipid raft hypothesis postulates that cholesterol can drive the formation of ordered domains within the plasma membrane of cells, which may serve as platforms for cell signalling and membrane trafficking. There is now a wealth of evidence for these domains. However, their study has hitherto been hampered by the resolution limit of optical microscopy, making the definition of their properties problematic and contentious. (...) New microscopy techniques circumvent the resolution limit and, for the first time, allow the fluorescence imaging of structures on length scales below 200 nm. This review describes such techniques, particularly as applied to the study of membrane organisation, synthesising newly emerging facets of lipid raft biology into a state‐of‐the art model.Editor's suggested further reading in BioEssays: Super‐resolution imaging prompts re‐thinking of cell biology mechanisms Abstract and Quantitative analysis of photoactivated localization microscopy (PALM) datasets using pair‐correlation analysis Abstract. (shrink)

Fluorescence imaging has become an indispensable tool in cell and molecular biology. GFP‐like fluorescent proteins have revolutionized fluorescence microscopy, giving experimenters exquisite control over the localization and specificity of tagged constructs. However, these systems present certain drawbacks and as such, alternative systems based on a fluorogenic interaction between a chromophore and a protein have been developed. While these systems are initially designed as fluorescent labels, they also present new opportunities for the development of novel labeling and detection strategies. (...) This review focuses on new labeling protocols, actuation methods, and biosensors based on fluorogenic protein systems. (shrink)

Six years ago, the Singer lab published a landmark paper which described how individual mRNA particles cross the nuclear pore complex in mammalian tissue culture cells. This involved the simultaneous imaging of mRNAs, each labeled by a large number of tethered fluorescent proteins and fluorescently tagged nuclear pore components. Now two groups have applied this technique to the budding yeast Saccharomyces cerevisiae. Their results indicate that in the course of nuclear export, mRNAs likely engage complexes that are present on (...) either side of the pore and that these interactions are modulated by proteins present in the messenger ribonucleoprotein (mRNP) complex. These findings lend support to the notion that just before and/or after the completion of nuclear export, mRNPs undergo one or more maturation steps that prepare the packaged mRNAs for translation. These results represent new and exciting insights into the mechanism of mRNA nuclear export. (shrink)

Embryos and microscopes share a long, remarkable history and biologists have always been intrigued to watch how embryos develop under the microscope. Here we discuss the advances in microscopy which have greatly influenced our current understanding of embryogenesis. We highlight the evolution of microscopes and the optical technologies that have been instrumental in studying various developmental processes. These imaging modalities provide mechanistic insights into the dynamic cellular and molecular events which drive lineage commitment and morphogenetic changes in the developing embryo. (...) We begin the journey with a brief history of microscopy to study embryos. First, we review the principles and optics of light, fluorescence, confocal, and electron microscopy which have been key techniques for imaging cellular and molecular events during embryonic development. Next, we discuss recent key imaging modalities such as light‐sheet microscopy, which are suitable for whole embryo imaging. Further, we highlight imaging techniques like multiphoton and super resolution microscopy for beyond light diffraction limit, high resolution imaging. Lastly, we review some of the scattering‐based imaging methods and techniques used for imaging human embryos. (shrink)

Macromolecular interactions play a central role in many biological processes. Protein‐protein interactions have mostly been studied by co‐immunoprecipitation, which cannot provide quantitative information on all possible molecular connections present in the complex. We will review a new approach that allows cellular proteins and biomolecular complexes to be studied in real‐time at the single‐molecule level. This technique is called single‐molecule pull‐down (SiMPull), because it integrates principles of conventional immunoprecipitation with the powerful single‐molecule fluorescence microscopy. SiMPull is used to count how many (...) of each protein is present in the physiological complexes found in cytosol and membranes. Concurrently, it serves as a single‐molecule biochemical tool to perform functional studies on the pulled‐down proteins. In this review, we will focus on the detailed methodology of SiMPull, its salient features and a wide range of biological applications in comparison with other biosensing tools. (shrink)

While innovations in modern microscopy, spectroscopy, and nanoscopy techniques have made single molecule observation a standard in many laboratories, the actual design of meaningful fluorescence reporter systems now hinders major scientific breakthroughs. Even though the field of chemical biology is supercharging the fluorescence toolbox, surprisingly few strategies exist that make the transition from model systems to biologically relevant applications. At the same time, the number of microscopy techniques is growing dramatically. We explain our view on how the impact of modern (...) technologies is influenced not only by further hard‐ and software developments, but also by the availability and suitability of protein‐engineering tools. We identify how the largely independent research fields of chemical biology and fluorescence nanoscopy can influence each other to synergistically drive future technology that can visualize the localization, structure, and dynamics of molecular function without constraints. (shrink)

Herculaneum papyri found during the discovery of the Villa dei Papiri in the XVIII century are our only knowledge about Greek philosophical schools. Unfortunately, the original manuscripts are in a precarious state of conservation and the currently available editions of them have largely been made obsolete by the latest technological progress. The aim of the Advanced Grant ERC project ‘Greekschools’ is to provide a new protocol based on optical methods to increase the text reading and thus allow for a new (...) critical edition of the whole treatise of Philodemus’ "Arrangement of the Philosophers". A multi-disciplinary approach is adopted and non-invasive techniques to Herculaneum papyri investigations such as Macro X-Ray Fluorescence Imaging (MA-XRF), Shortwave-Infrared Hyperspectral Imaging (SWIR), high resolution digital microscopy and Technical Photography were applied to read the text hidden on the verso, detect, classify, and replace overlapping layers and read the text concealed inside them. In this work some first preliminary results will be reported. (shrink)

New imaging methodologies in quantitative fluorescence microscopy, such as Förster resonance energy transfer (FRET), have been developed in the last few years and are beginning to be extensively applied to biological problems. FRET is employed for the detection and quantification of protein interactions, and of biochemical activities. Herein, we review the different methods to measure FRET in microscopy, and more importantly, their strengths and weaknesses. In our opinion, fluorescence lifetime imaging microscopy (FLIM) is advantageous for detecting inter‐molecular interactions quantitatively, the (...) intensity ratio approach representing a valid and straightforward option for detecting intra‐molecular FRET. Promising approaches in single molecule techniques and data analysis for quantitative and fast spatio‐temporal protein‐protein interaction studies open new avenues for FRET in biological research. (shrink)

Conformational changes of proteins and other biomolecules play a fundamental role in their functional mechanism. Single pair Förster resonance energy transfer offers the possibility to detect these conformational changes and dynamics, and to characterize their underlying kinetics. Using spFRET on microscopes with different modes of detection, dynamic timescales ranging from nanoseconds to seconds can be quantified. Confocal microscopy can be used as a means to analyze dynamics in the range of nanoseconds to milliseconds, while total internal reflection fluorescence microscopy offers (...) information about conformational changes on timescales of milliseconds to seconds. While the existence of dynamics can be directly inferred from the FRET efficiency time trace or the correlation of FRET efficiency and fluorescence lifetime, additional computational approaches are required to extract the kinetic rates of these dynamics, a short overview of which is given in this review. The functional mechanism of proteins is often driven by underlying conformational changes. These intramolecular changes and dynamics can be investigated using single pair Förster resonance energy transfer. The kinetic timescales of the dynamics in the range of nanoseconds to seconds is then quantified using different experimental and analytical implementations. (shrink)

A recent article argued that signals from conventional Raman spectroscopy of organic materials are overwhelmed by edge filter and fluorescence artefacts. The article targeted a subset of Raman spectroscopic investigations of fossil and modern organisms and has implications for the utility of conventional Raman spectroscopy in comparative tissue analytics. The inferences were based on circular reasoning centered around the unconventional analysis of spectra from just two samples, one modern, and one fossil. We validated the disputed signals with in situ Fourier‐Transform (...) Infrared (FT‐IR) Spectroscopy and through replication with different lasers, filters, and operators in independent laboratories. Our Raman system employs a holographic notch filter which is not affected by edge filter or other artefacts. Multiple lines of evidence confirm that conventional Raman spectra of fossils contain biologically and geologically meaningful information. Statistical analyses of large Raman and FT‐IR spectral data sets reveal patterns in fossil composition and yield valuable insights into the history of life. (shrink)

Fluorescence microscopy is a powerful tool used in scientific and medical research, but it is inextricably linked to phototoxicity. Neglecting phototoxicity can lead to erroneous or inconclusive results. Recently, several reports have addressed this issue, but it is still underestimated by many researchers, even though it can lead to cell death. Phototoxicity can be reduced by appropriate microscopic techniques and carefully designed experiments. This review focuses on recent strategies to reduce phototoxicity in microscopic imaging of living cells and tissues. We (...) describe digital image processing and new hardware solutions. We point out new modifications of microscopy methods and hope that this review will interest microscopy hardware engineers. Our aim is to underscore the challenges and potential solutions integral to the design of microscopy systems. Simultaneously, we intend to engage biologists, offering insight into the latest technological advancements in imaging that can enhance their understanding and practice. (shrink)

Fluorescent in situ hybridization technology is one of the most exciting and versatile research tools to be developed in recent years. It has enabled research to progress at a phenomenal rate in diverse areas of basic research as well as in clinical medicine. Fluorescent in situ hybridization has applications in physical mapping, the study of nuclear architecture and chromatin packaging, and the investigation of fundamental principles of biology such as DNA replication, RNA processing, gene amplification, gene integration and (...) chromatin elimination. This review highlights some of these areas and provides source material for the reader who seeks more information on a specific field. (shrink)

There is a bustling, fluorescent clamor that governs hospital hallways during the day and so fills the air that any sound wanting attention has to vie for it, each alarm louder and more cacophonous than the last. But at night, an altogether different temper settles over the hospital. A restrained, low-lit quiet descends, transforming those long corridors into a space that seems smaller and almost comforting. Almost any sound stands out at night. I was once trudging down one of (...) those subdued nighttime hallways after many busy hours on call, allowing the glimpse of sleeping patients in each passing room to give me hope for a nap that night, too. My head was down and my thoughts were elsewhere, but the .. (shrink)

If quantum mechanics is interpreted as an objective, complete, physical theory, applying to macroscopic as well as microscopic systems, then the linearity of quantum dynamics gives rise to the measurement problem and related problems, which cannot be solved without modifying the dynamics. Eight desiderata are proposed for a reasonable modified theory. They favor a stochastic modification rather than a deterministic non-linear one, but the spontaneous localization theories of Ghirardi et al. and Pearle are criticized. The intermittent fluorescence of a trapped (...) atom irradiated by two laser beams suggests a stochastic theory in which the locus of stochasticity is interaction between a material system and the electromagnetic vacuum. (shrink)

This paper explores the use of new scientific techniques to examine collections of historic scientific apparatus and other technological artefacts. One project under discussion uses interferometry to examine the history of lens development, while another uses X-ray fluorescence to discover the kinds of materials used to make early mathematical and astronomical instruments. These methods lead to surprising findings: instruments turn out to be fake, and lens makers turn out to have been adept at solving the riddle of aperture. Although exciting, (...) in some ways this is neither novel nor particularly unusual. After all, lab techniques have been used in art and archaeological collections for a very long time. In fact, scientific instruments themselves have been examined in this way since at least the 1950s. What, then, is special about the use of new instruments to examine old instruments? We argue that the answer has less to do with measuring historical innovation or establishing priority, and more to do with networks of craft know-how that, typically, have left no other historical traces than those embodied in surviving instruments themselves. We show, in particular, how collections of objects can be mobilised within wider histories of knowledge, placing instruments within a dynamic interplay of craft knowledge, expertise, labour, commerce, and material exchange, over the longue durée. Finally, we suggest that these kinds of lab analyses can be given an extra dimension through the use of computational modelling, and we introduce the “Tools of Knowledge” project, which is designed to bring together XRF with techniques from the digital humanities, in order to tell a new story about the development of scientific instruments from the 16th to the 20th century. (shrink)

Many individuals on the autism spectrum are hypersensitive to certain sensory stimuli. For this group, as well as for non-autistic individuals with sensory processing disorders, being exposed to e.g. fluorescent lights, perfume odours, and various sounds and noises can be real torment. In this article, I consider the normative implications of such offence for the design of office spaces, which is a topic that has not received any attention from philosophers. After identifying different ways in which the senses of (...) hypersensitive workers might be protected within these spaces, I show that many of such accommodations can be made at reasonable cost, before arguing that doing so ought to be a legal requirement. (shrink)

Cet article constitue le second volet d'un programme d'ensemble sur le Néolithique de la Thessalie. Il est consacré aux résultats des analyses chimiques et pétrographiques effectuées sur la céramique de la fin de la culture de Sesklo («Néolithique Moyen») et du début de la culture de Dimini («Néolithique Récent»). Environ 400 analyses, principalement en fluorescence X, sont présentées ici, sur un total d'un millier déjà réalisées. Elles portent à la fois sur la céramique fine, la céramique grossière et sur des (...) prélèvements d'argile naturelle. Les résultats concernent d'une part la définition chimique, pétrographique et technologique des groupes céramiques précédemment reconnus d'un point de vue stylistique (BCH 112 [1988]) et d'autre part le mode de production et de circulation de ces différentes catégories. Trois modèles peuvent être distingués. La céramique grossière est essentiellement produite localement sur chaque site et circule peu. Les différents styles peints sont produits localement, mais circulent dans des proportions importantes entre les sites. Enfin la céramique «gris-sur- gris», techniquement remarquable, est produite dans une zone très limitée du Nord-Ouest thessalien, mais diffusée dans l'ensemble de la Thessalie. L'artisanat céramique se révèle ainsi beaucoup plus complexe qu'on ne le supposait habituellement; l'on peut également mieux cerner la constitution des entités culturelles du Néolithique. (shrink)

Advances in biochemistry, chemistry and engineering have enabled the development of a new gene expression assay. This ‘chip‐based’ approach utilizes microscopic arrays of cDNAs printed on glass as high‐density hybridization targets. Fluorescent probe mixtures derived from total cellular messenger RNA (mRNA) hybridize to cognate elements on the array, allowing accurate measurement of the expression of the corresponding genes. Array densities of >1,000 cDNAs per cm2 enable quantitative expression monitoring of a large number of genes in a single hybridization. A (...) two‐color fluorescence detection scheme allows rapid and simultaneous differential expression analysis of independent biological samples. Mass‐produced microarrays provide a new tool for genome expression analysis that may revolutionize genetic dissection, drug discovery and human disease diagnostics. (shrink)

Between Summits I and II, media ethics established its legitimacy, summarized into recommendations for the field's future fluorescence. This history points to the challenges through which media ethics moves to another order of magnitude. A historical map of media ethics scholarship since 1980 divides into 5 domains, and each is introduced: theory, social philosophy, religious ethics, technology, and truth. From this content analysis of the literature, an agenda emerges for research and academic study that can raise media ethics to a (...) higher level. (shrink)

Model organisms, the use of green fluorescent proteins, and orthogonal transfer RNA are examples of artificial causes being used in biology. Recent work characterizing the research interests of biologists in terms of a common set of values has ruled out artificial causes as biologically interesting. For instance, Kenneth Waters argues that biologists are primarily interested in causes that actually obtain. Similarly, Marcel Weber argues that biologists are primarily concerned with biologically normal interventions. Both views express a widely received attitude (...) about the interests and goals of biologists as being primarily concerned with the contingent facts of our world. While I agree with this general attitude about the contingent nature of biology, I argue that neither view fully accounts for the diversity that distinguishes the discipline. Along with actual and biologically normal causes, biologists are also interested in artificial causes for technological and observational purposes. I maintain that research interest in artificial causes provides some pragmatic reasons for thinking that research programs in cellular biology aren’t driven by a common core set of values. (shrink)

A toy is a valuable medium for promoting parent-child interaction. This study selected six light-emitting or reflective materials to produce composite toy balls, and conducted tests on 15 families with preschool-aged high-functioning autistic children. Quantification method I analysis was employed in the study, and the experimental results indicated that the metal ball was the representative sample that elicited many smiles or laughs and much finger pointing as well as high levels of pleasure and activeness.; the mitball was the representative sample (...) that provoked much eye contact, produced satisfactory reactions to activities,; the quality of fluorescence enhanced the levels of pleasure and the reactions to the activity. We propose that dynamic and reflective materials can be adopted to divert the attention of children, and fluorescent toys can then employed to sustain parent-child interaction. (shrink)

The mitochondrion is known as the “powerhouse” of eukaryotic cells since it is the main site of adenosine 5′‐triphosphate (ATP) production. Using a temperature‐sensitive fluorescent probe, it has recently been suggested that the stray free energy, not captured into ATP, is potentially sufficient to sustain mitochondrial temperatures higher than the cellular environment, possibly reaching up to 50 °C. By 50 °C, some DNA and mitochondrial proteins may reach their melting temperatures; how then do these biomolecules maintain their structure and (...) function? Further, the production of reactive oxygen species (ROS) accelerates with temperature, implying higher oxidative stresses in the mitochondrion than generally appreciated. Herein, it is proposed that mitochondrial heat shock proteins (particularly Hsp70), in addition to their roles in protein transport and folding, protect mitochondrial proteins and DNA from thermal and ROS damage. Other thermoprotectant mechanisms are also discussed. (shrink)

Although debates over carbon taxes and trading schemes, over carbon offsets and compact fluorescents are important, our efforts to address the environmental challenges that we face will fall short unless and until we also set about the difficult work of reconceiving who we are and how we are related to our processive cosmos. What is needed, I argue, are new ways of thinking and acting grounded in new ways of understanding ourselves and our relationship to the world, ways of understanding (...) that recognize our fundamental interdependence and interconnection with everyone and everything in the cosmos, ways of understanding that recognize the intrinsic beauty and value of every form of existence. What is needed, I suggest, is a moral philosophy grounded in Alfred North Whitehead's philosophy of organism. It is the primary aim of this essay to defend the value of a moral philosophy inspired by Whitehead's organic, beauty-centered conception of reality. (shrink)

In eukaryotic cells the nucleus and its contents are separated from the cytoplasm by the nuclear envelope. Macromolecules, as well as smaller molecules and ions, can cross the nuclear envelope through the nuclear pore complex. Molecules greater than approx. 60 kDa and containing a nuclear localization signal are actively transported across the nuclear membranes, but there has been little evidence for regulatory mechanisms for smaller molecules and ions. Recently, diffusion across the nuclear envelope has been observed to be regulated by (...) nuclear cisternal Ca2+ concentrations. Following depletion of Ca2+ from the nuclear store by inositol 1,4,5‐trisphosphate or Ca2+ chelators, a fluorescent 10 kDa marker molecule was no longer able to enter the nucleus. Distinct conformational states of the nuclear pore complexes depended on the Ca2+ filling state of the nuclear envelope, supporting the assumption that a switch in the conformation of the nuclear pore complex may control the transport of intermediate‐sized molecules across the nuclear envelope. Thus nuclear Ca2+ stores may regulate the conformational state of the nuclear pore complex, and thereby passive diffusion of molecules between the cytosol and the nucleoplasm. The physiological significance of this finding is currently unknown. (shrink)

Modern aesthetic Minimalism is neither a flight to abstract spirituality, nor an extracting process of a primordial essence. It is concerned, rather, with the aesthetic object as pure refiguration and the production of “concrete universality”, of form as content and possibility of itself. This becomes especially apparent in the Minimalism of the 1960s. The main focus of this paper will be on Dan Flavin’s luminous minimalism. The latter is characterised by a style that, though simple in appearance, introduced a higher (...) level of complexity with regard to the relation between form and matter, concept and thing, in artistic production. Neither sculptures nor paintings, Flavin’s works fall right under Donald Judd’s category of “specific objects”. Nevertheless, his luminous creations are not particularly specific, just as they are not strictly speaking objects. Their main material – colour-light – is as intangible and diffuse, as its origin – the fluorescent lamp – is commonplace and artificial. Drawing on such influential theorists of art as Theodor W. Adorno, Peter Bürger, Clement Greenberg and Jacques Rancière, this paper studies the lessons that philosophy can learn from Flavin's light minimalism, most notably in relation to the notions of aesthetic materiality and sublimation. (shrink)

Brigitte Bourgeois and Philippe Jockey Gold and Marble: the Gilded Hellenistic Sculptures of Delos p. 331-349 The investigation we are conducting on the polychromy of the Hellenistic sculptures of Delos has enabled us to add to the corpus of gilded marble works and to refine the typology. A visual examination of the sculptures through a video-microscope, combined with an analysis of the remains isolated by this means under X-fluorescence, has revealed the existence of three large types of gold leaf gilding (...) on marble at Delos in around 100 BC: totally gilded statues, works on which the gilding forms only an added colouring to the general polychromy, and works that we propose to call "chrysochromes", which present a singularity not hitherto recognised of a very bright polychromy on the clothed parts associated with gold on the nude parts. Among the number of important results of this enquiry may be counted the revelation of the overall gilding on the Delian copy in the National Museum at Athens of the Polyclitus Diadumenus, carved and gilded in imitation of a gilt bronze or even a gold statue. Such a use of gold leaf gilding on the Delos marbles calls in any case for a reconsideration of the question of the reception in antiquity of such works, as well as of such a success of gold at Delos and no doubt elsewhere in the Greek world in the same period. (shrink)

Gap junction intercellular communication channels permit the exchange of small regulatory molecules and ions between neighbouring cells and coordinate cellular activity in diverse tissue and organ systems. These channels have short half‐lives and complex assembly and degradation pathways. Much of the recent work elucidating gap junction biogenesis has featured the use of connexins (Cx), the constituent proteins of gap junctions, tagged with reporter proteins such as Green Fluorescent Protein (GFP) and has illuminated the dynamics of channel assembly in live (...) cells by high‐resolution time‐lapse microscopy. With some studies, however, there are potential short‐comings associated with the GFP chimeric protein technologies. A recent report by Gaietta et al., has highlighted the use of recombinant proteins with tetracysteine tags attached to the carboxyl terminus of Cx43, which differentially labels ‘old’ and ‘new’ connexins thus opening up new avenues for studying temporal and spatial localisation of proteins and in situ trafficking events.1 BioEssays 24:876–880, 2002. © 2002 Wiley Periodicals, Inc. (shrink)

Since most of the functions in cells are mediated by multimeric protein complexes, the determination of protein–protein interactions is an important step in the study of cellular mechanisms. Traditionally, after screening for possible target interactors by means of a yeast two‐hybrid screen, several methods are used to validate the initial result before carrying out functional experiments. Nowadays, non‐invasive fluorescence‐based methods like Bioluminescence Resonance Energy Transfer (BRET) and Fluorescence Resonance Energy Transfer (FRET) are widely used in the study of protein–protein interactions (...) in living cells. In the present review, we address the individual strengths and weaknesses of both RET approaches, providing information on their possible future use in the study of G protein‐coupled receptor oligomerization. BioEssays 30:82–89, 2008. © 2007 Wiley Periodicals, Inc. (shrink)