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Background: Medical imaging methods such as PET and MRI aid clinical assessment of Alzheimer’s disease (AD). Less expensive, less technically demanding, and more widely deployable technologies are needed to expand objective screening for diagnosis, treatment, and research. We previously reported brain tissue near-infrared optical spectroscopy (NIR) in vitro indicating the potential to meet this need. Objective: To determine whether completely non-invasive, clinical, NIR in vivo can distinguish AD patients from age-matched controls and to show the potential of NIR as a clinical screen and monitor of therapeutic efficacy. Methods: NIR spectra were acquired in vivo. Three groups were studied: autopsy-confirmed AD, control and mild cognitive impairment (MCI). A feature selection approach using the first derivative of the intensity normalized spectra was used to discover spectral regions that best distinguished “AD-alone” (i.e., without other significant neuropathology) from controls. The approach was then applied to other autopsy-confirmed AD cases and to clinically diagnosed MCI cases. Results: Two regions about 860 and 895 nm completely separate AD patients from controls and differentiate MCI subjects according to the degree of impairment. The 895 nm feature is more important in separating MCI subjects from controls (ratio-of-weights: 1.3); the 860 nm feature is more important for distinguishing MCI from AD (ratio-of-weights: 8.2). Conclusion: These results form a proof of the concept that near-infrared spectroscopy can detect and classify diseased and normal human brain in vivo. A clinical trial is needed to determine whether the two features can track disease progression and monitor potential therapeutic interventions.

Gulf War illness (GWI) is a chronic illness with no known validated biomarkers that affects the lives of hundreds of thousands of people. As a result, there is an urgent need for the development of an untargeted and unbiased method to distinguish GWI patients from non-GWI patients. We report on the application of laser-induced breakdown spectroscopy (LIBS) to distinguish blood plasma samples from a group of subjects with GWI and from subjects with chronic low back pain as controls. We initially obtained LIBS data from blood plasma samples of four GWI patients and four non-GWI patients. We used an analytical method based on taking the difference between a mean LIBS spectrum obtained with those of GWI patients from the mean LIBS spectrum of those of the control group, to generate a “difference” spectrum for our classification model. This model was cross-validated using different numbers of differential LIBS emission peaks. A subset of 17 of the 82 atomic and ionic transitions that provided 70% of correct diagnosis was selected test in a blinded fashion using 10 additional samples and was found to yield 90% classification accuracy, 100% sensitivity, and 83.3% specificity. Of the 17 atomic and ionic transitions, eight could be assigned unambiguously to species of Na, K, and Fe.

We established a unique platform for proteomic analysis of cultured three-dimensional (3D) neurons and brain tissue from Alzheimer's disease (AD) patients. We collected peripheral blood mononuclear cells (PBMC), converted PBMC to induced pluripotent stem cell (iPSC) lines, and differentiated the iPSC into human 3D neuro-spheroids. The postmortem brain tissue from the superior frontal cortex, inferior frontal cortex and cerebellum area of the AD patients was compared to the same regions from the control subjects. Proteomic analysis of 3D neuro-spheroids derived from AD subjects revealed the alteration of a number of proteins involved in axon growth, mitochondrial function, and antioxidant defense. Similar analysis of post-mortem AD brain tissue revealed significant alteration in proteins involved in oxidative stress, neuro-inflammation, along with proteins related to axonal injury. These results clearly indicate that the dysfunction of 3D neurons from AD patients in our in vitro environment is comparable to the post-mortem AD brain tissue in vivo. In conclusion, our study revealed a number of candidate proteins that have important implications in AD pathogenesis and supports the notion that the iPSC-derived 3D neuronal system functions as a model to examine novel aspects of AD pathology. Significance In this study, we present a unique platform for proteomic analysis of induced pluripotent stem cell-derived three dimensional (3D) neurons and compare the results to those from three regions of post-mortem brain tissue from Alzheimer's disease patients and normal control subjects. Our results show that the dysfunction of 3D neurons from AD patients in our in vitro environment is comparable to the post-mortem AD brain tissue in vivo. Our results revealed several candidate proteins that have important implications in AD pathogenesis.

The testing of candidate drugs to slow progression of Alzheimer's disease (AD) requires clinical trials that are lengthy and expensive. Efforts to model the biochemical milieu of the AD brain may be greatly facilitated by combining two cutting edge technologies to generate three-dimensional (3D) human neuro-spheroid from induced pluripotent stem cells (iPSC) derived from AD subjects. We created iPSC from blood cells of five AD patients and differentiated them into 3D human neuronal culture. We characterized neuronal markers of our 3D neurons by immunocytochemical staining to validate the differentiation status. To block the generation of pathologic amyloid β peptides (Aβ), the 3D-differentiated AD neurons were treated with inhibitors targeting β-secretase (BACE1) and γ-secretases. As predicted, both BACE1 and γ-secretase inhibitors dramatically decreased Aβ generation in iPSC-derived neural cells derived from all five AD patients, under standard two-dimensional (2D) differentiation conditions. However, BACE1 and γ-secretase inhibitors showed less potency in decreasing Aβ levels in neural cells differentiated under 3D culture conditions. Interestingly, in a single subject AD1, we found that BACE1 inhibitor treatment was not able to significantly reduce Aβ42 levels. To investigate underlying molecular mechanisms, we performed proteomic analysis of 3D AD human neuronal cultures including AD1. Proteomic analysis revealed specific reduction of several proteins that might contribute to a poor inhibition of BACE1 in subject AD1. To our knowledge, this is the first iPSC-differentiated 3D neuro-spheroid model derived from AD patients' blood. Our results demonstrate that our 3D human neuro-spheroid model can be a physiologically relevant and valid model for testing efficacy of AD drug.

Esophageal cancer is increasing in frequency in the United States faster than any other cancer. Barrett's esophagus, an otherwise benign complication of esophageal reflux, affects approximately three million Americans and precedes almost all cases of esophageal cancer. If detected as high-grade dysplasia (HGD), most esophageal cancers can be prevented. Standard-of-care screening for dysplasia uses visual endoscopy and a prescribed pattern of biopsy. This procedure, in which a tiny fraction of the affected tissue is selected for pathological examination, has a low probability of detection because dysplasia is highly focal and visually indistinguishable. We developed a system called endoscopic polarized scanning spectroscopy (EPSS), which performs rapid optical scanning and multispectral imaging of the entire esophageal surface and provides diagnoses in near real time. By detecting and mapping suspicious sites, guided biopsy of invisible, precancerous dysplasia becomes practicable. Here we report the development of EPSS and its application in several clinical cases, one of which merits special consideration.

Gold nanorods have the potential to be employed as extremely bright molecular marker labels for fluorescence, absorption, or scattering imaging of living tissue. However, samples containing a large number of gold nanorods usually exhibit relatively wide spectral lines. This linewidth limits the use of the nanorods as effective molecular labels, since it would be rather difficult to image several types of nanorod markers simultaneously. In addition, the observed linewidth does not agree well with theoretical calculations, which predict significantly narrower absorption and scattering lines. The discrepancy could be explained by apparent broadening because of the contribution of nanorods with various sizes and aspect ratios. We measured native scattering spectra of single gold nanorods with the confocal light absorption and scattering spectroscopy system, and found that single gold nanorods have a narrow spectrum as predicted by the theory, which suggests that nanorod-based molecular markers with controlled narrow aspect ratios, and to a lesser degree size distributions, should provide spectral lines sufficiently narrow for effective biomedical imaging.

A long-standing impediment for applications of optical techniques in cellular biology is the inability to characterize subcellular structures whose dimensions are much less than about 1 /spl mu/m. In this paper, we describe a method based on light scattering spectroscopy that can find the size distribution of subcellular organelles as small as 100 nm with an accuracy of 20 nm. We report experiments using aqueous suspensions of subcellular organelles enriched in mitochondria, zymogen granules, and microsomes. From the observed light scattering spectra, we extract size distributions that are in excellent agreement with the results of electron microscopy. Further studies are underway to extract the shapes of organelles in addition to their sizes.

The Zα domain of human double-stranded RNA adenosine deaminase 1 binds specifically to left-handed Z-DNA and stabilizes the Z-conformation. Here we report spectroscopic and analytical results that demonstrate that Zα can also stabilize the left-handed Z-conformation in double-stranded RNA. Zα induces a slow transition from the right-handed A-conformation to the Z-form in duplex r(CG) 6 , with an activation energy of 38 kcal mol −1 . We conclude that Z-RNA as well as Z-DNA can be accommodated in the tailored binding site of Zα. The specific binding of Z-RNA by Zα may be involved in targeting double-stranded RNA adenosine deaminase 1 for a role in hypermutation of RNA viruses.

Surface enhancement factors of at least ${10}^{12}$ for the Raman scattering of single-walled carbon nanotubes in contact with fractal silver colloidal clusters result in measuring very narrow Raman bands corresponding to the homogeneous linewidth of the tangential C--C stretching mode in semiconducting nanotubes. Normal and surface-enhanced Stokes and anti-Stokes Raman spectra are discussed in the framework of selective resonant Raman contributions of semiconducting or metallic nanotubes to the Stokes or anti-Stokes spectra, respectively, of the population of vibrational levels due to the extremely strong surface-enhanced Raman process, and of phonon-phonon interactions.

The purpose of this study was to investigate whether near-infrared (NIR) fluorescence spectroscopy could be used to detect Alzheimer's disease (AD) by brain tissue autofluorescence. Unfixed temporal cortex specimens from AD cases and age-matched, non-AD controls were frozen at autopsy and then thawed just prior to spectral measurement. Spectra of intrinsic tissue fluorescence induced by 647 nm light were recorded from 650 to 850 nm. We used principal component analysis of the tissue spectra from 17 AD cases and 5 non-AD control cases in a calibration study to establish a diagnostic algorithm. Retrospectively applied to the calibration set, the algorithm correctly classified 23 of 24 specimens. In a prospective study of 19 specimens from 5 AD brains and 2 non-AD control brains, 3 of the 4 control specimens and all AD specimens were correctly diagnosed. Both the excitation light used and the measured brain tissue autofluorescence are at NIR wavelengths that can propagate through skull and overlying tissue. Therefore, our results demonstrate an optical spectroscopic technique that carries direct molecular level information about disease. This is the first step toward a clinical tool that has the potential to be applied to the noninvasive diagnosis of AD in living patients.

In agreement with previous results reported for colloidal silver clusters, effective surface-enhanced Raman cross sections of about 10-16 cm2 per molecule, corresponding to enhancement factors on the order of 10 14, have also been obtained for molecules attached to colloidal gold clusters. Spatially isolated nearly spherical colloidal gold particles of about 60 nm size show maximum enhancement factors on the order of 103 at 514 nm excitation, close to the single plasmon resonance. The enhancement factor increases by eleven orders of magnitude when colloidal gold clusters are formed by aggregation of the gold colloids and when near-infrared excitation is applied. The large effective surface-enhanced Raman cross section has been estimated by a straightforward method based on steady-state population redistribution due to the pumping of molecules to the first excited vibrational state via the strongly enhanced Raman process. Our experimental finding confirms the important role of colloidal clusters for extremely large surface-enhanced Raman scattering (SERS) enhancement factors. Simultaneously, it suggests colloidal gold clusters as a substrate for high-sensitivity surface-enhanced Raman scattering, which can provide an enhancement level sufficient for Raman single molecule detection. Due to its chemical inactivity, gold might have some advantages compared to silver, particularly in biomedical spectroscopy.

The outcomes of the clinical trials of the γ-secretase inhibitor Semagacestat (LY-450139) and the γ-secretase modulator (GSM) Tarenflurbil were disappointing, but may not represent the end of the γ-secretase era. γ-Secretase modulators, by definition, only block the γ-secretase cleavage of amyloid-β protein precursor (AβPP) to generate the longer, 42-residue amyloid-β (Aβ42) without changing the production of total Aβ. The first generation GSMs were shown to block Aβ42 generation while increasing Aβ38. The non-steroidal anti-inflammatory drug, Tarenflurbil, binds to AβPP and shifts the cleavage site from Aβ42 to Aβ38. In addition, Tarenflurbil does not affect the γ-secretase cleavage of Notch. Even before the failed clinical trials of Tarenflurbil, second generation GSMs had emerged, and some of these GSMs interact with presenilin, which carries the active site of the γ-secretase. While second generation GSMs are pharmacologically superior to first generation GSMs, in vivo Aβ profiles (decreased levels of Aβ38, Aβ40, and Aβ42) in animals treated with potent GSMs are strikingly different from those in cultured cells. Thus, the unique pharmacologic properties of new GSMs and their mechanisms of action need to be elucidated in order to avoid the fate of Tarenflurbil. It is critical to understand how GSMs shift the "end" in vivo, i.e., shifting the γ-secretase cleavage at the C-terminal end of Aβ. In view of the myriad effects of candidate GSMs on Aβ production in cells and animals, drug development would benefit from better definition of the target-GSM interaction and physiological function of shorter Aβ peptides.

We present a spectroscopic microscopy system for measuring transmission and reflectance from erythrocytes. Spectroscopic markers are used to distinguish between fetal and adult cells for the application of genetic screening from maternal blood.

A double-integrating-sphere system measures the absorption and scattering coefficients of brown and white fat. The optical spectroscopic properties of the fat tissue are sensitive to the pathophysiological conditions of mice.

We report development of coherent CLASS microscopy which provides dramatically higher spectral contrast compared to the existing incoherent technique. It can non-invasively monitor subcellular dynamics without the need for exogenous agents.

This article reports the evolution of scanning spectral imaging techniques using scattered light for minimally invasive detection of early cancerous changes in tissue and cell biology applications. Optical spectroscopic techniques have shown promising results in the diagnosis of disease on a cellular scale. They do not require tissue removal, can be performed in vivo, and allow for real time diagnoses. Fluorescence and Raman spectroscopy are most effective in revealing molecular properties of tissue. Light scattering spectroscopy (LSS) relates the spectroscopic properties of light elastically scattered by small particles, such as epithelial cell nuclei and organelles, to their size, shape and refractive index. It is capable of characterizing the structural properties of tissue on cellular and sub-cellular scales. However, in order to be useful in the detection of early cancerous changes which are otherwise not visible to the naked eye, it must rapidly survey a comparatively large area while simultaneously detecting these cellular changes. Both goals are achieved by combining LSS with spatial scanning imaging. Two examples are described in this article. The first reviews a clinical system for screening patients with Barrett's esophagus. The second presents a novel advancement in confocal light absorption and scattering spectroscopic (CLASS) microscopy.

Endoscopic polarized scanning spectroscopic imaging provides real time information about morphology of epithelial tissue in gastrointestinal tract. This technique could lead to in vivo detection of invisible dysplasia in Barrett’s esophagus.

This letter reports the development of an endoscopic polarized scanning spectroscopy (EPSS) instrument compatible with existing endoscopes. This instrument uses light scattering spectroscopy (LSS). In proof-of-principle studies using a single-point instrument, LSS has successfully demonstrated the ability to identify pre-cancer in the epithelial tissues of five different organs, including Barrett's esophagus (BE). The EPSS instrument can provide real time in vivo information on the location of otherwise invisible high grade dysplasia (HGD), a predictor of adenocarcinoma, and thus can serve as a guide for biopsy. It should greatly reduce the time and labor involved in performing screening and obtaining diagnoses, cause less patient discomfort and ensure that fewer biopsies are required for the reliable location of pre-cancerous lesions.

Present techniques for prenatal diagnosis are invasive and present significant risks of fetal loss. Noninvasive prenatal diagnosis utilizing fetal nucleated red blood cells (fNRBC) circulating in maternal peripheral blood has received attention, since it poses no risk to the fetus. However, because of the failure to find broadly applicable identifiers that can differentiate fetal from adult NRBC, reliable detection of viable fNRBC in amounts sufficient for clinical use remains a challenge. In this Letter we show that fNRBC light-scattering spectroscopic signatures may lead to a clinically useful method of minimally invasive prenatal genetic testing.

We have developed a novel optical method for observing submicron intracellular structures in living cells which is called confocal light absorption and scattering spectroscopic (CLASS) microscopy. It combines confocal microscopy, a well-established high-resolution microscopic technique, with light scattering spectroscopy (LSS). CLASS microscopy requires no exogenous labels and is capable of imaging and continuously monitoring individual viable cells, enabling the observation of cell and organelle functioning at scales on the order of 100 nm. In addition, it provides not only size information but also information about the biochemical and physical properties of the cell.

The molecular bases of Alzheimer disease and related neurodegenerative disorders are becoming better understood, but the means for definitive diagnosis and monitoring in vivo remain lacking. Near-infrared optical spectroscopy offers a potential solution. We acquired transmission and reflectance spectra of thin brain tissue slabs, from which we calculated wavelength-dependent absorption and reduced scattering coefficients from 470-1000 nm. The reduced scattering coefficients in the near infrared clearly differentiated Alzheimer from control specimens. Diffuse reflectance spectra of gross brain tissue in vitro confirmed this observation. These results suggest a means for diagnosing and monitoring Alzheimer disease in vivo, using near-infrared optical spectroscopy.

Nanorods have the potential to be employed as bright molecular biomedical labels. However, nanorod samples usually exhibit relatively wide spectral lines. Using CLASS microscopy we found that single gold nanorods have a narrow spectrum.

We describe a new scanning microscopy technique, phase-dispersion microscopy (PDM). The technique is based on measuring the phase difference between the fundamental and the second-harmonic light in a novel interferometer. PDM is highly sensitive to subtle refractive-index differences that are due to dispersion (differential optical path sensitivity, 5 nm). We apply PDM to measure minute amounts of DNA in solution and to study biological tissue sections. We demonstrate that PDM performs better than conventional phase-contrast microscopy in imaging dispersive and weakly scattering samples.

This article reports the development of an optical imaging technique, confocal light absorption and scattering spectroscopic (CLASS) microscopy, capable of noninvasively determining the dimensions and other physical properties of single subcellular organelles. CLASS microscopy combines the principles of light-scattering spectroscopy (LSS) with confocal microscopy. LSS is an optical technique that relates the spectroscopic properties of light elastically scattered by small particles to their size, refractive index, and shape. The multispectral nature of LSS enables it to measure internal cell structures much smaller than the diffraction limit without damaging the cell or requiring exogenous markers, which could affect cell function. Scanning the confocal volume across the sample creates an image. CLASS microscopy approaches the accuracy of electron microscopy but is nondestructive and does not require the contrast agents common to optical microscopy. It provides unique capabilities to study functions of viable cells, which are beyond the capabilities of other techniques.

We recently developed a new microscopic optical technique capable of noninvasive analysis of cell structure and cell dynamics on the submicron scale [1]. It combines confocal microscopy, a well-established high-resolution microscopic technique, with light scattering spectroscopy (LSS) and is called confocal light absorption and scattering spectroscopic (CLASS) microscopy. CLASS microscopy requires no exogenous labels and is capable of imaging and continuously monitoring individual viable cells, enabling the observation of cell and organelle functioning at scales on the order of 100 nm. To test the ability of CLASS microscopy to monitor cellular dynamics in vivo we performed experiments with human bronchial epithelial cells treated with DHA and undergoing apoptosis. The treated and untreated cells show not only clear differences in organelle spatial distribution but time sequencing experiments on a single cell show disappearance of certain types of organelles and change of the nuclear shape and density with the progression of apoptosis. In summary, CLASS microscopy provides an insight into metabolic processes within the cell and opens doors for the noninvasive real-time assessment of cellular dynamics. Noninvasive monitoring of cellular dynamics with CLASS microscopy can be used for a real-time dosimetry in a wide variety of medical and environmental applications that have no immediate observable outcome, such as photodynamic therapy, drug screening, and monitoring of toxins.

We recently developed a novel optical method for observing submicron intracellular structures in living cells which is called confocal light absorption and scattering spectroscopic (CLASS) microscopy. It combines confocal microscopy, a well-established high-resolution microscopic technique, with light scattering spectroscopy (LSS). CLASS microscopy requires no exogenous labels and is capable of imaging and continuously monitoring individual viable cells, enabling the observation of cell and organelle functioning at scales on the order of 100 nm with 10 nm accuracy. To demonstrate the ability of the CLASS microscope to monitor unstained living cells on submicrometer scale we studied human bronchial epithelial cells undergoing apoptosis. Fluorescence microscopy of living cells requires application of molecular markers which can affect normal cell functioning. CLASS microscopy is not affected by this avoiding potential interference of fluorescence molecular markers with cell processes. In addition, it provides not only size information but also information about the biochemical and physical properties of the cell. CLASS microscopy can provide unique capabilities for the study of cell interactions with the environment, cell reproduction and growth and other functions of viable cells, which are inaccessible by other techniques.

We report the development of a novel optical imaging technique, confocal light scattering spectroscopic microscopy, capable of non-invasively determining the dimensions and other physical properties of single subcellular organelles with 5 nm accuracy.

Introduction: Light Scattering Spectroscopy has been a recently developed as a non-invasive technique capable of sizing the cellular organelles. With this technique, we monitor the heat-induced sub-cellular structural transformations in a human RPE cell culture. Material and Methods: A single layer of human RPE cells (ATCC) was grown on a glass slide. Cells are illuminated with light from a fiber-coupled broadband tungsten lamp. The backscattered (180 degree) light spectra are measured with an optical multichannel analyzer (OMA). Spectra are measured during heating of the sample. Results: We reconstructed the size distribution of sub-micron organelles in the RPE cells and observed temperaturerelated changes in the scattering density of the organelles in the 200-300nm range (which might be peroxisomes, microsomes or lysosomes). The sizes of the organelles did not vary with temperature, so the change in scattering is most probably due to the change in the refractive indexes. As opposed to strong spectral variation with temperature, the total intensity of the backscattered light did not significantly change in the temperature range of 32-49 °C. Conclusion: We demonstrate that Light Scattering Spectroscopy is a powerful tool for monitoring the temperatureinduced sub-cellular transformations. This technique providing an insight into the temperature-induced cellular processes and can play an important role in quantitative assessment of the laser-induced thermal effects during retinal laser treatments, such as Transpupillary Thermal Therapy (TTT), photocoagulation, and Photodynamic Therapy (PDT).

Neurodegenerative pathologies such as Alzheimer's disease present protein aggregates that scatter light. We are developing techniques to detect their characteristic spectra in vivo as a basis for definitive, non-invasive diagnosis and for monitoring experimental therapeutics.

We report light scattering experiments using aqueous suspensions of subcellular organelles. From the observed spectra, we extract size distributions that are in very agreement with the results of electron microscopy studies.

Alzheimer’s disease is the most common dementing disorder. Its neuropathological hallmarks are senile plaques and various forms of neurofibrillary pathology. We are developing a light scattering spectroscopy optical technique, which will identify differences in the absorption and light scattering properties of brain tissue due to the presence of senile plaques and neurofibrillary tangles and detect both chemical and morphological changes in Alzheimer’s brain at the earliest possible stages.

The Zalpha domain of human double-stranded RNA adenosine deaminase (ADAR1) has been crystallized with a hexanucleotide containing alternating deoxyribose and ribose furanose sugars. Solution circular dichroism experiments show that this double-stranded chimera (dCrG)(3) initially adopts the right-handed A-conformation. However, addition of stoichiometric amounts of Zalpha causes a rapid transition to the Z-conformation. Raman spectroscopy of crystals of the Zalpha-(dCrG)(3) complex confirm that the chimeric oligonucleotide is stabilized in the Z-conformation. A complete data set has been obtained at 2.5 A resolution. The Zalpha-(dCrG)(3) crystals belong to the tetragonal I422 space group, with unit-cell parameters a = b = 104.2, c = 117.6 A. Work is under way to solve the structure by molecular replacement.

Raman spectroscopy is a potentially important clinical tool for real-time diagnosis of disease and in situ evaluation of living tissue. The purpose of this article is to review the biological and physical basis of Raman spectroscopy of tissue, to assess the current status of the field and to explore future directions. The principles of Raman spectroscopy and the molecular level information it provides are explained. An overview of the evolution of Raman spectroscopic techniques in biology and medicine, from early investigations using visible laser excitation to present-day technology based on near-infrared laser excitation and charge-coupled device array detection, is presented. State-of-the-art Raman spectrometer systems for research laboratory and clinical settings are described. Modern methods of multivariate spectral analysis for extracting diagnostic, chemical and morphological information are reviewed. Several in-depth applications are presented to illustrate the methods of collecting, processing and analysing data, as well as the range of medical applications under study. Finally, the issues to be addressed in implementing Raman spectroscopy in various clinical applications, as well as some long-term directions for future study, are discussed.

hexagons of the structure with respect to the nanotube axis. SWNT’s also exhibit remarkable Raman spectra, which can provide a wealth of information about the one dimensional (1-D) electronic density of states through a strong resonant coupling between the incident and scattered photons and the electronic transitions between the van Hove singularities in the 1-D density of states in the valence and conduction bands. Through the wide range of laser frequencies available in the Raman Laboratory of the Spectroscopy Laboratory, it has been possible to carry out resonance Raman experiments at many laser excitation energies, thereby allowing study of many novel features. Figure 2 shows the Raman spectrum of a carbon nanotube sample over a wide frequency range. The strong feature at ~155 cm -1 is associated with the radial breathing mode, in which every carbon atom vibrates in phase in the radial direction. Since the radial breathing frequency is proportional to

The proteolytically defined Z-DNA binding domain Za of human adenosine deaminase type 1 (hADAR1) has been crystallized in complex with the DNA oligomer d(TCGCGCG). The crystals were obtained from a solution containing ammonium sulfate as precipitating agent and belong to the tetragonal space group P4212. A complete diffraction data set has been collected to a resolution of 2.4 Å. The unit-cell dimensions are a = b = 85.9, c = 71.3 Å. A Raman spectrum of the complex indicates that the DNA in the complex adopts the left-handed Z conformation.

Gold nanorods can be used as extremely bright labels for differential light scattering measurements using two closely spaced wavelengths, thereby detecting human disease through several centimeters of tissue in vivo. They have excellent biocompatibility, are non-toxic, and are not susceptible to photobleaching. They have narrow, easily tunable plasmon spectral lines and thus can image multiple molecular targets simultaneously. Because of their small size, gold nanorods can be transported to various tissues inside the human body via the vasculature and microvasculature, and since they are smaller than vascular pore sizes, they can easily cross vascular space and enter individual cells.

Attempts to realize the important potential of gold nanorods as extremely bright molecular markers have been limited by the broad spectroscopic linewidths usually observed. We identify the origin of this broadening as inhomogeneous broadening due to the extreme sensitivity of the surface plasmon resonance to the nanorod aspect ratio. Using confocal light scattering spectroscopic microscopy, we observed the narrow homogeneously broadened plasmon lines of single gold nanorods and obtained the first quantitative measurements of this homogeneous broadening. We show that homogeneous broadening can be predicted from first principals.

We have developed a novel optical method for observing submicrometer intracellular structures in living cells, which is called confocal light absorption and scattering spectroscopic (CLASS) microscopy. It combines confocal microscopy, a well-established high-resolution microscopic technique, with light-scattering spectroscopy. CLASS microscopy requires no exogenous labels and is capable of imaging and continuously monitoring individual viable cells, enabling the observation of cell and organelle functioning at scales of the order of 100 nm.

Zero‐field optically detected magnetic resonance (ODMR) and resonance Raman spectroscopy are used to study the adsorbate/substrate system chlorophyll b on highly oriented pyrolytic graphite. Chlorophyll b was applied to the conductive basal surface of the graphite using Langmuir–Blodgett techniques in which both the chlorophyll–chlorophyll and chlorophyll–graphite spacing could be varied. ODMR data reveal changes in chlorophyll b triplet state dynamic features which in the isolated molecule are determined by spin‐orbit coupling mechanisms. The possibility of energy transfer among adsorbed species is also suggested. These results are shown to depend not only upon the distance of the molecule from the surface, but also upon the intermolecular distance of photoexcited adsorbates. The resonance Raman spectrum leads to a plausible orientation of the adsorbed chlorophyll unit with respect to the graphite surface.

The zero-field fluorescence-detected triplet state magnetic resonance spectra have been obtained for the pyrochlorophyllide a—apomyoglobin complex at 2 K. The triplet state zero-field splittings and spin sublevel dynamics were detected on the resolved features of the structured low-temperature fluorescence. Structured fluorescence is not observed for pyrochlorophylide a in an organic matrix under identical conditions. These data are interpreted in terms of the local binding site of the pyrochlorophyllide a chromophore in the protein and the low-temperature conformation of the protein matrix.

The zero field triplet state spin transitions of chlorophyll b have been measured by monitoring the microwave induced intensity changes of bands in the resonance Raman spectrum. The magnitude of the effect is found to be comparable to that observed in fluorescence detected ODMR.