bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of a Commercial Integrating Sphere Setup for the Determination of Absolute Photoluminescence Quantum Yields of Dilute Dye Solutions
Authors: Würth Christian , Lochmann Cornelia , Spieles Monika , Pauli Jutta , Hoffmann Katrin , Schüttrigkeit Tanja , Franzl Thomas , Resch-Genger Ute
Published: October 2010

The commercial availability of stand-alone setups for the determination of absolute photoluminescence quantum yields (Φf) in conjunction with the increasing use of integrating sphere accessories for spectrofluorometers is expected to have a considerable influence not only on the characterization of chromophore systems for use in optical and opto-electronic devices, but also on the determination of this key parameter for (bio)analytically relevant dyes and functional luminophores. Despite the huge potential of systems measuring absolute Φf values and the renewed interest in dependable data, evaluated protocols for even the most elementary case, the determination of the fluorescence quantum yield of transparent dilute solutions of small organic dyes with integrating sphere methods, are still missing. This encouraged us to evaluate the performance and sources of uncertainty of a simple commercial integrating sphere setup with dilute solutions of two of the best characterized fluorescence quantum yield standards, quinine sulfate dihydrate and rhodamine 101, strongly differing in spectral overlap between absorption and emission. Special attention is dedicated to illustrate common pitfalls of this approach, thereby deriving simple procedures to minimize measurement uncertainties and improve the comparability of data for the broad community of users of fluorescence techniques.
Identification of a Mixed Microparticle by Combined Microspectroscopic Techniques: A Real Forensic Case Study in the Biopharmaceutical Industry
Authors: Cao Xiaolin , Masatani Peter , Torraca Gianpiero , Wen Zai-Qing
Published: October 2010

Identification of foreign microparticles in drug products is one of the first steps in evaluating the nature of particle contamination and its consequences for product quality. To characterize various foreign particles, we use spectral database search methods as well as a number of microscopic and microspectroscopic techniques. Here, we report a case study involving the identification and root-cause investigation of a microparticle consisting of four compounds. Foreign microparticles consisting of mixtures pose unique challenges for identification as their spectra are difficult to interpret and general database searches usually return unsatisfactory results. Moreover, sample separation through purification and other manipulations is time consuming and often difficult for these microparticles due to their small sizes and the limited quantities of the components. Here we demonstrate an applicable methodology that combines multiple microscopic and microspectroscopic techniques to identify a heterogeneous microparticle without the need for sample purification or chemical separation. This methodology primarily combines Raman, infrared, and energy dispersive X-ray microspectroscopic techniques to obtain complementary spectral information for the identification of heterogeneous particles. With this methodology, the mixed microparticle investigated in this study was determined to consist of polyisobutylene, hydrated magnesium silicate, titanium dioxide, and silica, likely originating from the vial stopper material.
Experimental Study of NaCl Aqueous Solutions by Raman Spectroscopy: Towards a New Optical Sensor
Authors: Đuričković Ivana , Marchetti Mario , Claverie Rémy , Bourson Patrice , Chassot Jean-Marie , Fontana Marc D.
Published: October 2010

Raman spectroscopy was used to study the NaCl aqueous solutions around the solid-liquid phase transition. Special attention was devoted to the modification induced by the salt on the OH stretching band of water. Investigations were carried out in the temperature range between-21 and 10 °C, for concentrations from 0 to 200 g/L. We demonstrated that micro-Raman spectroscopy can be used as a marker, allowing the determination of the salt concentration of an aqueous solution with an error close to ±5%.
Stopped-Flow Ultra-Rapid-Scanning Fourier Transform Infrared Spectroscopy on the Millisecond Time Scale
Authors: Reback Matthew L. , Roske Christopher W. , Bitterwolf Thomas E. , Griffiths Peter R. , Manning Christopher J.
Published: October 2010

Full-range mid-infrared spectra were measured during the reaction of CpCo(CO)2 with nitrosyl chloride by interfacing a rapid-mixing stopped-flow device with an ultra-rapid-scanning Fourier transform infrared (FT-IR) spectrometer having a temporal resolution of 5 ms. Changes to the data acquisition hardware of this spectrometer now allow a sequence of well over 2000 spectra to be collected without interruption. Two transient species were observed spectroscopically during the first 500 ms of the reaction of CpCo(CO)2 with nitrosyl chloride. The shortest-lived species that was observed, [CpCo(CO)2(NO)]+, had a half-life of ∼20 ms at 25 °C and ∼70 ms at 10 °C. This intermediate transformed into a longer-lived (∼0.5 s) intermediate, CpCo(NO)Cl. Potential intermediate species with one CO and one NO ligand, such as [CpCo(CO)(NO)]+ and CpCo(CO)(NO)Cl, were not observed, although the possibility that they exist cannot be ruled out.
Surface-Enhanced Raman Scattering Detection and Tracking of Nanoprobes: Enhanced Uptake and Nuclear Targeting in Single Cells
Authors: Gregas Molly K. , Scaffidi Jonathan P. , Lauly Benoit , Vo-Dinh Tuan
Published: October 2010

We describe the development and application of a co-functionalized nanoprobe and biodelivery platform combining a nuclear targeting peptide (NTP) for improved cellular uptake and intracellular targeting with p-mercaptobenzoic acid (pMBA) as a surface-enhanced Raman scattering (SERS) reporter for tracking and imaging. The nuclear targeting peptide, an HIV-1 protein-derived TAT sequence, has been previously shown to aid entry of cargo through the cell membrane via normal cellular processes, and furthermore, to localize small cargo to the nucleus of the cell. Previous work in our lab has verified cell uptake and distribution of the nanoprobes in clinically relevant mouse and human cell lines. In this work, two-dimensional SERS mapping was used to track the spatial and temporal progress of nanoparticle uptake in PC-3 human prostate cells and to characterize localization at various time points, demonstrating the potential for an intracellularly targeted multiplexed nanobiosensing system with excellent sensitivity and specificity. Silver nanoparticles co-functionalized with the TAT peptide showed greatly enhanced cellular uptake over the control nanoparticles lacking the targeting moiety. The ability to detect and monitor nanoprobe trafficking using SERS spectroscopy offers an improved alternative over previous tracking and detection methods such as light microscopy and fluorescence methods. The development of multifunctional nanoconstructs for intracellular delivery has potential clinical applications in early detection and selective treatment of disease in affected cells. Other applications include use in basic research aimed at understanding the inner workings of living cells and how they respond to chemical and biological stimuli.
Detection of Cotton Lint Trash within the Ultraviolet—Visible Spectral Range
Authors: Zhou Fei , Ding Tianhuai
Published: October 2010

Cotton lint trash is a serious problem in the textile industry. The principle upon which this research is based is that different materials have different spectral absorption, excitation, and emission characteristics. Although white-light imaging is widely used to detect colored foreign-matter contaminants, or “trash”, it is almost useless for detecting white trash. The objective of the research described in this paper was to achieve the best trash detection result possible in the spectral range from 250 to 850 nm. Diffuse reflection spectroscopy indicated that the differences in gray value between lint and white trash become significant in the ultraviolet (UV) range, especially from 250 to 350 nm. Fluorescence spectroscopy gave reliable evidence that the UV-induced fluorescence intensity of white trash is much stronger than that of lint. To detect several types of trash simultaneously, the interaction of white-light imaging and UV-induced fluorescence imaging was studied. To avoid the spectral interference caused by white light in fluorescence imaging, a novel method—an alternating imaging detection method—is proposed. Experiments indicated that the advantages of both white-light imaging and UV-induced fluorescence imaging were preserved in the method. The novel method could effectively detect both colored and white trash in real time. This method can also be applied to trash detection in seed cotton, wool, tea leaf, and tobacco leaf.
Conformation of Poly(Ethylene Oxide) Chains in Clay Galleries
Authors: Zhou Hu , Lai Zuliang , Wu Peiyi
Published: October 2010

The conformation and arrangement of poly(ethylene oxide) (PEO) chains in clay galleries is still controversial. In our work, various spectroscopic methods have been used to explore the conformation of PEO in clay galleries. The melt intercalation process is investigated using variable-temperature Raman spectroscopy. It is found that the sharp peak at 860 cm−1 appears with an increase of the intercalation time, suggesting the formation of a crown-ether-like association between the cations and the PEO oxygen atoms. Two-dimensional infrared correlation analysis also suggests the presence of the crown-ether-like association between them. Therefore, a distorted helical conformation may be a more accurate way to describe the conformation of the PEO chains in the clay galleries, and a single-layer arrangement is suggested.
Heterogeneous Thermal-Lens Immunoassay for Small Organic Compounds: Determination of 4-Aminophenol
Authors: Nedosekin Dmitrya , Brusnichkin Anton V. , Luk'Yanov Andrei Y. , Eremin Sergei A. , Proskurnin Mikhail A.
Published: October 2010

4-Aminophenol was selected as a model hapten for thermal-lens detection in a heterogeneous indirect immunoassay for small organic compounds. The assay is based on the competition of the free hapten and 4-aminophenol labeled with tetramethyl rhodamine isothiocyanate (TRITC) for rabbit anti-4-aminophenol antibodies (4-AP-GA-BSA) immobilized on a transparent poly(ethylene terephthalate) plate. The amount of the colored analyte was directly measured by thermal lensing at the plate surface. The developed method is specific for 4-aminophenol. The limit of detection is 2 × 10−7M, which corresponds to the absolute amount of 3 × 10−11mol of 4-aminophenol. The sensitivities of the developed thermal-lens and fluorescence-based measurements of the immunoassay under the same conditions are in good agreement with the expected and discussed theoretical sensitivities of photothermal and fluorescence measurements.
Fourier Transform Infrared Microspectroscopy of Endocarditis Vegetation
Authors: Batard Eric , Jamme Frédéric , Boutoille David , Jacqueline Cédric , Caillon Jocelyne , Potel Gilles , Dumas Paul
Published: October 2010

The objectives of this work were to compare the infrared spectra of bacterial endocarditis vegetation with those of native valvular tissue and the infrared spectra of vegetation bacterial masses with those of surrounding vegetation tissue. Streptococcal aortic endocarditis was induced in three rabbits. Vegetation slices were cryo-sectioned for study by Fourier transform infrared (FT-IR) microspectroscopy. Valvular apparatus, vegetation, and bacterial masses within the vegetation were localized on hematoxylin and eosin (H&E) stained contiguous slices. Infrared images of whole vegetations and images of bacterial masses were acquired with apertures set to 80 × 80 and 20 × 20 μm, respectively. Valvular apparatus and vegetation showed different infrared spectra, mainly in the amide I and amide II bands (1674–1518 cm−1), and at about 1450, 1400, 1340, 1280, 1240, 1200, 1080, and 1030 cm−1. Valvular collagen, elastin, and proteoglycans may explain these differences. Bacterial masses and surrounding vegetation showed different infrared patterns, mainly in the amide I and amide II bands and in the 1142–991 cm−1 carbohydrate spectral range. Bacterial nucleic acids and polysaccharides may partly explain these differences. Study of experimental endocarditis vegetation using FT-IR microspectroscopy distinguishes (1) the vegetation from the valvular tissue, and (2) the bacterial masses from the surrounding tissue. This study demonstrates for the first time that FT-IR microspectroscopy is able to detect bacterial growth in infected tissue. FT-IR microspectroscopy appears to be a useful tool for investigation of the biochemical structure of endocarditis vegetation.
Directed Calcium Chloride Coalescence Method for Preparation of Silver Nanocubes
Authors: Xia Lixin , Jia Yi , Liu Guangye , Li Jushi , Sun Mengtao
Published: October 2010

Controlling the size, shape, and structure of metal nanoparticles is very important because of the strong correlation between these parameters and their resulting optical, electrical, and catalytic properties. This paper describes a directed calcium chloride coalescence method, based upon incubating a silver colloid with an aqueous solution of CaCl2, for preparation of silver nanocubes with a particle size of 270 to 950 nm. The method avoids the use of nonvolatile surfactants and polymers, which may be adsorbed onto the silver nanocubes and interfere with their possible applications in catalysis and analytical devices based on surface-enhanced Raman scattering (SERS) spectroscopy. The nanocubes show good SERS activity in the presence of adsorbed 4-mercaptobenzoic acid (4-MBA) with excitation at 632.8 nm, and the enhancement factor reaches ∼7 × 105. The nanocubes are produced in a simple and cost-effective way, and they are expected to play an important role in the development of SERS-based analytical devices. The method may represent a novel route for preparation of metal nanocubes, which is a subject of intense interest.
Use of Spectra in the Visible and Near-Mid-Ultraviolet Range with Principal Component Analysis and Partial Least Squares Processing for Monitoring of Suspended Solids in Municipal Wastewater Treatment Plants
Authors: Lourenço Nídia D. , Paixão Fátima , Pinheiro Helena M. , Sousa Alexandra
Published: October 2010

The present work assesses the possibility of using spectrophotometry in the near-mid-ultraviolet and visible wavelength ranges (282–790 nm) for the direct monitoring of treatment performance in municipal wastewater treatment plants (WWTPs). Principal component analysis (PCA) was used to analyze spectral data from samples collected along three WWTP process lines with different primary and secondary treatment units. The clustering observed in PCA score plots was mainly attributed to the suspended solids fraction present in the wastewater and highlighted differences in solids quality between plants and along the treatment lines. Thus, satisfactory partial least squares (PLS) calibration models to estimate total suspended solids (TSS) values from the acquired spectra could only be established per plant. The PLS models were established using 1–2 factors, with root mean error of cross-validation and coefficient of determination values in the 50–86 mg TSS L−1 and 82–95% ranges, respectively.
Optimal Choice of Baseline Correction for Multivariate Calibration of Spectra
Authors: Liland Kristian Hovde , Almøy Trygve , Mevik Bjørn-Helge
Published: October 2010

Baselines are often chosen by visual inspection of their effect on selected spectra. A more objective procedure for choosing baseline correction algorithms and their parameter values for use in statistical analysis is presented. When the goal of the baseline correction is spectra with a pleasing appearance, visual inspection can be a satisfactory approach. If the spectra are to be used in a statistical analysis, objectivity and reproducibility are essential for good prediction. Variations in baselines from dataset to dataset means we have no guarantee that the best-performing algorithm from one analysis will be the best when applied to a new dataset. This paper focuses on choosing baseline correction algorithms and optimizing their parameter values based on the performance of the quality measure from the given analysis. Results presented in this paper illustrate the potential benefits of the optimization and points out some of the possible pitfalls of baseline correction.
Simultaneous Optical Spectroscopic Measurement of Hemoglobin and Myoglobin Saturations and Cytochrome aa3 Oxidation in vivo
Authors: Arakaki Lorilee S. L. , Ciesielski Wayne A. , Thackray Brett D. , Feigl Eric O. , Schenkman Kenneth A.
Published: October 2010

A method to simultaneously measure oxygenation in vascular, intracellular, and mitochondrial spaces from optical spectra acquired from muscle has been developed. In order to validate the method, optical spectra in the visible and near-infrared regions (600–850 nm) were acquired from solutions of myoglobin, hemoglobin, and cytochrome oxidase that included Intralipid as a light scatterer. Spectra were also acquired from the rabbit forelimb. Three partial least squares (PLS) analyses were performed on second-derivative spectra, each separately calibrated to myoglobin oxygen saturation, hemoglobin oxygen saturation, or cytochrome aa3 oxidation. The three variables were measured from in vitro and in vivo spectra that contained all three chromophores. In the in vitro studies, measured values of myoglobin saturation, hemoglobin saturation, and cytochrome aa3 oxidation had standard errors of 5.9%, 7.4%, and 12.2%, respectively, with little cross-talk between the in vitro measurements. In the progression from normal oxygenation to ischemia in the rabbit forelimb, hemoglobin desaturated first, followed by myoglobin, while cytochrome aa3 reduction occurred last. The ability to simultaneously measure oxygenations in the vascular, intracellular, and mitochondrial compartments will be valuable in physiological studies of muscle metabolism and in clinical studies when oxygen supply or utilization are compromised.
A Neutron Resonance Capture Analysis Experimental Station at the ISIS Spallation Source
Authors: Pietropaolo Antonino , Gorini Giuseppe , Festa Giulia , Reali Enzo , Grazzi Francesco , Schooneveld Erik M.
Published: October 2010

Neutron resonance capture analysis (NRCA) is a nuclear technique that is used to determine the elemental composition of materials and artifacts (e.g., bronze objects) of archaeological interest. NRCA experiments are mostly performed at the GELINA facility in Belgium, a pulsed neutron source operating with an electron linear accelerator. Very intense fluxes of epithermal neutrons are also provided by spallation neutron sources, such as the ISIS spallation neutron source in the United Kingdom. In the present study, the suitability of the Italian Neutron Experimental Station (INES) beam line for NRCA measurements is assessed using a compact ( n, γ) resonance detector made of a Yttrium–Aluminum–Perovskite (YAP) scintillation crystal coupled with a silicon photomultiplier (SiPM) readout. The measurements provided a qualitative recognition of the composition of the standard sample, a lower limit for the sensitivity for NRCA for almost-in-traces elements, and an estimation of the relative isotopic concentration in the sample.
Determination of Organic and Inorganic Carbon in Forest Soil Samples by Mid-Infrared Spectroscopy and Partial Least Squares Regression
Authors: Tatzber Michael , Mutsch Franz , Mentler Axel , Leitgeb Ernst , Englisch Michael , Gerzabek Martin H.
Published: October 2010

Analyses of organic and inorganic carbon are of great interest in the field of soil analyses. Soil samples from a national monitoring project were provided for this study, including more than 130 forest sites from Austria. We investigated the humus layers (if present undecomposed litter (L), of mixed samples of F- (intermediate decomposed organic matter) and H-(highly decomposed organic matter) (FH)) and upper mineral soil layers (0–5 and 5–10 cm) of the samples. Mid-infrared spectra were recorded and evaluated by their band areas; subsequently we calculated models with the partial least squares approach. This was done by correlating calculated data of the mid-infrared spectra with gas-volumetrically determined carbonate values and measurements of organic carbon from an elemental analyzer. For carbonate determination, this approach gave satisfying results. For measurements of organic carbon, it was necessary to discriminate into humus layers and mineral soils or even more groups to obtain satisfactory correlations between spectroscopically determined and conventionally measured values. These additional factors were the presence of carbonate, the forest type, and the dominant tree species. In mineral soils, fewer subdivisions were necessary to obtain useful results. In humus layers, groupings of sites with more similar characteristics had to be formed in order to obtain satisfying results. The conclusion is that the chemical background of soil organic matter leading to different proportions of functional groups, especially in the less humified organic matter of the humus layers, plays a key role in analyses with mid-infrared spectroscopy. Keeping this in mind, the present approach has a significant potential for the prediction of properties of forest soil layers, such as, e.g., carbonate and organic carbon contents.
Drop Coating Deposition Raman Spectroscopy of Fluorescein Isothiocyanate Labeled Protein
Authors: Zhang Dongmao , Vangala Karthikeshwar , Jiang Dongping , Zou Sige , Pechan Tibor
Published: October 2010

Using bovine serum albumin (BSA) as the model protein, normal Raman spectra of fluorescein isothiocyanate (FITC) conjugated protein were systematically studied for the first time using both solution and the drop coating deposition Raman (DCDR) sampling techniques. The FITC-BSA Raman spectra are dominated by the FITC Raman features that are strongly pH dependent. Current DCDR detection sensitivity obtained with a 10:1 FITC-BSA conjugate is 45 fmol in terms of total protein consumption and ∼15 attomol at laser probed volume. Unlike the FITC-BSA solution Raman spectra, where the FITC Raman features are photostable, concurrent FITC fluorescence and Raman photobleaching is observed in the DCDR spectra of FITC-BSA. While the FITC Raman photobleaching follows a single exponential decay function with a time constant independent of the FITC labeling ratio, the fluorescence background photobleaching is much more complicated and it depends strongly on the FITC labeling ratio and sample conditions. Mechanistically, the FITC Raman photobleaching is believed to be due to photochemical reaction of the FITC molecules in the electronically excited state. The FITC fluorescence photobleaching involves both concentration quenching and photochemical quenching, and the latter may involve a photochemical intermediate that is fluorescence inactive but Raman active.
First Steps of in situ Surface-Enhanced Raman Scattering during Shipboard Experiments
Authors: Péron Olivier , Rinnert Emmanuel , Colas Florent , Lehaitre Michel , Compère Chantal
Published: October 2010

It is shown that the surface-enhanced Raman scattering (SERS) technique can be applied to detect organic molecules during in situ experiments. To this purpose, we used trans-1,2-bis(4-pyridyl)ethylene (BPE) as a target molecule. Adsorbed on the SERS chemosensor surface and excited under laser, the vibration modes of the molecules can be identified. SERS chemosensors are based on quartz substrates functionalized by silanization and partially coated with gold nanoparticles. SERS measurements during shipboard experiments were made with a home-made in situ Raman spectrometer connected to a marinized micro-fluidic system. The device was designed to host chemosensors in order to ensure measurements with a flow cell. A theoretical limit of detection was estimated in the range of picomolar (pM) concentrations based on Freundlich isotherm calculations.
A Study of Glutathione Molecules Adsorbed on Silver Surfaces under Different Chemical Environments by Surface-Enhanced Raman Scattering in Combination with the Heat-Induced Sensing Method
Authors: Huang Genin Gary , Han Xiao X. , Hossain Mohammad Kamal , Kitahama Yasutaka , Ozaki Yukihiro
Published: October 2010

In this study, surface-enhanced Raman scattering (SERS) in combination with a heat-induced sensing technique has been applied for investigating molecular orientations of glutathione molecules adsorbed on silver colloidal nanoparticles under different chemical environments, which has enabled us to further study how glutathione molecules are adsorbed on the silver surfaces. Factors that may affect the configurations of glutathione molecules adsorbed on the silver nanocolloids have been investigated. By observing the relative enhancement factors of SERS bands due to individual functional groups contributed from different terminals, the affinity between the different functional groups of glutathione and the silver surfaces under different conditions has been sorted and the orientations of glutathione molecules adsorbed on the silver surfaces have been investigated.
Qualitative Analysis Using Raman Spectroscopy and Chemometrics: A Comprehensive Model System for Narcotics Analysis
Authors: O'Connell Marie-Louise , Ryder Alan G. , Leger Marc N. , Howley Tom
Published: October 2010

The rapid, on-site identification of illicit narcotics, such as cocaine, is hindered by the diverse nature of the samples, which can contain a large variety of materials in a wide concentration range. This sample variance has a very strong influence on the analytical methodologies that can be utilized and in general prevents the widespread use of quantitative analysis of illicit narcotics on a routine basis. Raman spectroscopy, coupled with chemometric methods, can be used for in situ qualitative and quantitative analysis of illicit narcotics; however, careful consideration must be given to dealing with the extensive variety of sample types. To assess the efficacy of combining Raman spectroscopy and chemometrics for the identification of a target analyte under real-world conditions, a large-scale model sample system (633 samples) using a target (acetaminophen) mixed with a wide variety of excipients was created. Materials that exhibit problematic factors such as fluorescence, variable Raman scattering intensities, and extensive peak overlap were included to challenge the efficacy of chemometric data preprocessing and classification methods. In contrast to spectral matching analyte identification approaches, we have taken a chemometric classification model-based approach to account for the wide variances in spectral data. The first derivative of the Raman spectra from the fingerprint region (750–1900 cm−1) yielded the best classifications. Using a robust segmented cross-validation method, correct classification rates of better than ∼90% could be attained with regression-based classification, compared to ∼35% for SIMCA. This study demonstrates that even with very high degrees of sample variance, as evidenced by dramatic changes in Raman spectra, it is possible to obtain reasonably reliable identification using a combination of Raman spectroscopy and chemometrics. The model sample set can now be used to validate more advanced chemometric or machine learning algorithms being developed for the identification of analytes such as illicit narcotics.
Hydrogel Network Formation Revised: High-Resolution Magic Angle Spinning Nuclear Magnetic Resonance as a Powerful Tool for Measuring Absolute Hydrogel Cross-Link Efficiencies
Authors: Van Vlierberghe Sandra , Fritzinger Bernd , Martins José C. , Dubruel Peter
Published: October 2010

In the present work, high-resolution magic angle spinning (hr-MAS) NMR spectroscopy is applied as a straightforward nondestructive technique to quantify unreacted methacrylamide functionalities in cross-linked gelatin hydrogels. By adjusting several cross-linking parameters including the ultraviolet (UV) irradiation time and the photo-initiator concentration, the cross-linking degree can be easily varied. Remarkably, under all experimental conditions typically applied for hydrogel development, no more than 40% of the methacrylamide moieties present have reacted. The hr-MAS based approach to determine the cross-linking efficiency is shown to provide an innovative and more convenient alternative to the well-established classical techniques. In addition, the results obtained are in good correlation with mechanical analysis data.
A New Method to Obtain Fourier Transform Infrared Spectra Free from Water Vapor Disturbance
Authors: Chen Yujing , Wang Hai-Shui , Umemura Junzo
Published: October 2010

Infrared absorption bands due to water vapor in the mid-infrared regions often obscure important spectral features of the sample. Here, we provide a novel method to collect a qualified infrared spectrum without any water vapor interference. The scanning procedure for a single-beam spectrum of the sample is divided into two stages under an atmosphere with fluctuating humidity. In the first stage, the sample spectrum is measured with approximately the same number of scans as the background. If the absorbance of water vapor in the spectrum is positive (or negative) at the end of the first stage, then the relative humidity in the sample compartment of the spectrometer is changed by a dry (or wet) air blow at the start of the second stage while the measurement of the sample spectrum continues. After the relative humidity changes to a lower (or higher) level than that of the previously collected background spectrum, water vapor peaks will become smaller and smaller with the increase in scanning number during the second stage. When the interfering water lines disappear from the spectrum, the acquisition of a sample spectrum is terminated. In this way, water vapor interference can finally be removed completely.
Chemical Reduction Method for Preparation of Silver Nanoparticles on a Silver Chloride Substrate for Application in Surface-Enhanced Infrared Optical Sensors
Authors: Purna Gadupudi , Rao Chandra , Yang Jyisy
Published: October 2010

A new method for the preparation of silver nanoparticles (AgNPs) on silver chloride discs was developed to integrate the unique properties of plasmonic nanoparticles into infrared optical sensing technologies. AgNP layers exhibiting strong infrared surface enhancement were prepared by reacting silver chloride discs in a solution containing hydrazine, which acts as a reducing agent. The silver ions in the outer layer of the disc could be reduced under proper conditions and the reduced silver coagulated to form suitable AgNPs for surface-enhanced infrared absorption (SEIRA) measurements. To examine the influences of the reaction solution composition and also to optimize preparation of SEIRA substrates, factors such as pH value, reaction time, and concentration of reducing agent were examined. Results indicated that both the concentrations of hydrazine and hydroxide strongly influenced the SEIRA signals. The strongest signals were observed when AgNPs on a AgCl substrate were prepared by using a reducing solution of 20 mM NaOH with 0.75 mM hydrazine. Using the optimized substrates, intense SEIRA spectra were observed with an enhancement factor around two orders of magnitude compared to measurements made using conventional sampling techniques.
Sleep Deprivation Triggers Inducible Nitric Oxide-Dependent Nitric Oxide Production in Wake–Active Basal Forebrain Neurons
Authors: Kalinchuk Anna V. , McCarley Robert W. , Porkka-Heiskanen Tarja , Basheer Radhika
Published: October 2010

Sleep loss negatively impacts performance, mood, memory, and immune function, but the homeostatic factors that impel sleep after sleep loss are imperfectly understood. Pharmacological studies had implicated the basal forebrain (BF) inducible nitric oxide (NO) synthase (iNOS)-dependent NO as a key homeostatic factor, but its cellular source was obscure. To obtain direct evidence about the cellular source of iNOS-generated NO during sleep deprivation (SD), we used intracerebroventricular perfusion in rats of the cell membrane-permeable dye diaminofluorescein-2/diacetate (DAF-2/DA) that, once intracellular, bound NO and fluoresced. To circumvent the effects of neuronal NOS (nNOS), DAF-2/DA was perfused in the presence of an nNOS inhibitor. SD led to DAF-positive fluorescence only in the BF neurons, not glia. SD increased expression of iNOS, which colocalized with NO in neurons and, more specifically, in prolonged wakefulness-active neurons labeled by Fos. SD-induced iNOS expression in wakefulness-active neurons positively correlated with sleep pressure, as measured by the number of attempts to enter sleep. Importantly, SD did not induce Fos or iNOS in stress-responsive central amygdala and paraventricular hypothalamic neurons, nor did SD elevate corticosterone, suggesting that the SD protocol did not provoke iNOS expression through stress. We conclude that iNOS-produced neuronal NO is an important homeostatic factor promoting recovery sleep after SD.
Differential Patterns of Inputs Create Functional Zones in Central Nucleus of Inferior Colliculus
Authors: Loftus William C. , Bishop Deborah C. , Oliver Douglas L.
Published: October 2010

Distinct pathways carry monaural and binaural information from the lower auditory brainstem to the central nucleus of the inferior colliculus (ICC). Previous anatomical and physiological studies suggest that differential ascending inputs to regions of the ICC create functionally distinct zones. Here, we provide direct evidence of this relationship by combining recordings of single unit responses to sound in the ICC with focal, iontophoretic injections of the retrograde tracer Fluoro-Gold at the physiologically characterized sites. Three main patterns of anatomical inputs were observed. One pattern was identified by inputs from the cochlear nucleus and ventral nucleus of the lateral lemniscus in isolation, and these injection sites were correlated with monaural responses. The second pattern had inputs only from the ipsilateral medial and lateral superior olive, and these sites were correlated with interaural time difference (ITD)-sensitive responses to low frequency (<500 Hz). A third pattern had inputs from a variety of olivary and lemniscal sources, notably the contralateral lateral superior olive and dorsal nucleus of the lateral lemniscus. These were correlated with high-frequency ITD sensitivity to complex acoustic stimuli. These data support the notion of anatomical regions formed by specific patterns of anatomical inputs to the ICC. Such synaptic domains may represent functional zones in ICC.
Quantitative Analysis of Synaptic Vesicle Rabs Uncovers Distinct Yet Overlapping Roles for Rab3a and Rab27b in Ca2+-Triggered Exocytosis
Authors: Pavlos Nathan J. , Grønborg Mads , Riedel Dietmar , Chua John J. E. , Boyken Janina , Kloepper Tobias H. , Urlaub Henning , Rizzoli Silvio O. , Jahn Reinhard
Published: October 2010

Rab GTPases are molecular switches that orchestrate protein complexes before membrane fusion reactions. In synapses, Rab3 and Rab5 proteins have been implicated in the exo-endocytic cycling of synaptic vesicles (SVs), but an involvement of additional Rabs cannot be excluded. Here, combining high-resolution mass spectrometry and chemical labeling (iTRAQ) together with quantitative immunoblotting and fluorescence microscopy, we have determined the exocytotic (Rab3a, Rab3b, Rab3c, and Rab27b) and endocytic (Rab4b, Rab5a/b, Rab10, Rab11b, and Rab14) Rab machinery of SVs. Analysis of two closely related proteins, Rab3a and Rab27b, revealed colocalization in synaptic nerve terminals, where they reside on distinct but overlapping SV pools. Moreover, whereas Rab3a readily dissociates from SVs during Ca2+-triggered exocytosis, and is susceptible to membrane extraction by Rab-GDI, Rab27b persists on SV membranes upon stimulation and is resistant to GDI-coupled Rab retrieval. Finally, we demonstrate that selective modulation of the GTP/GDP switch mechanism of Rab27b impairs SV recycling, suggesting that Rab27b, probably in concert with Rab3s, is involved in SV exocytosis.
Nogo-A Stabilizes the Architecture of Hippocampal Neurons
Authors: Zagrebelsky Marta , Schweigreiter Rüdiger , Bandtlow Christine E. , Schwab Martin E. , Korte Martin
Published: October 2010

Although the role of myelin-derived Nogo-A as an inhibitor of axonal regeneration after CNS injury has been thoroughly described, its physiological function in the adult, uninjured CNS is less well known. We address this question in the hippocampus, where Nogo-A is expressed by neurons as well as oligodendrocytes. We used 21 din vitroslice cultures of neonatal hippocampus where we applied different approaches to interfere with Nogo-A signaling and expression and analyze their effects on the dendritic and axonal architecture of pyramidal cells. Neutralization of Nogo-A by function-blocking antibodies induced a major alteration in the dendrite structure of hippocampal pyramidal neurons. Although spine density was not influenced by Nogo-A neutralization, spine type distribution was shifted toward a more immature phenotype. Axonal complexity and length were greatly increased. Nogo-A KO mice revealed a weak dendritic phenotype resembling the effect of the antibody treatment. To discriminate a possible cell-autonomous role of Nogo-A from an environmental, receptor-mediated function, we studied the effects of short hairpin RNA-induced knockdown of Nogo-A or NgR1, a prominent Nogo-A receptor, within individual neurons. Knockdown of Nogo-A reproduced part of the dendritic and none of the spine or axon alterations. However, downregulation of NgR1 replicated the dendritic, the axonal, and the spine alterations observed after Nogo-A neutralization. Together, our results demonstrate that Nogo-A plays a major role in stabilizing and maintaining the architecture of hippocampal pyramidal neurons. Mechanistically, although the majority of the activity of Nogo-A relies on a receptor-mediated mechanism involving NgR1, its cell-autonomous function plays a minor role.
Smooth Operator: Avoidance of Subharmonic Bifurcations through Mechanical Mechanisms Simplifies Song Motor Control in Adult Zebra Finches
Authors: Elemans Coen P. H. , Laje Rodrigo , Mindlin Gabriel B. , Goller Franz
Published: October 2010

Like human infants, songbirds acquire their song by imitation and eventually generate sounds that result from complicated neural networks and intrinsically nonlinear physical processes. Signatures of low-dimensional chaos such as subharmonic bifurcations have been reported in adult and developing zebra finch song. Here, we use methods from nonlinear dynamics to test whether adult male zebra finches (Taenopygia guttata) use the intrinsic nonlinear properties of their vocal organ, the syrinx, to insert subharmonic transitions in their song. In contrast to previous data on the basis of spectrographic evidence, we show that subharmonic transitions do not occur in adult song. Subharmonic transitions also do not arise in artificially induced sound in the intact syrinx, but are commonly generated in the excised syrinx. These findings suggest that subharmonic transitions are not used to increase song complexity, and that the brain controls song in a surprisingly smooth control regimen. Fast, smooth changes in acoustic elements can be produced by direct motor control in a stereotyped fashion, which is a more reliable indicator of male fitness than abrupt acoustic changes that do not require similarly precise control. Consistent with this view is the presence of high fidelity at every level of motor control, from telencephalic premotor areas to superfast syringeal muscles.
Hyperpolarization-Activated Currents in Gonadotropin-Releasing Hormone (GnRH) Neurons Contribute to Intrinsic Excitability and Are Regulated by Gonadal Steroid Feedback
Authors: Chu Zhiguo , Takagi Hiroshi , Moenter Suzanne M.
Published: October 2010

Pulsatile release of gonadotropin-releasing hormone (GnRH) is required for fertility and is regulated by steroid feedback. Hyperpolarization-activated currents (Ih) play a critical role in many rhythmic neurons. We examined the contribution ofIhto the membrane and firing properties of GnRH neurons and the modulation of this current by steroid milieu. Whole-cell voltage- and current-clamp recordings were made of GFP-identified GnRH neurons in brain slices from male mice that were gonad-intact, castrated, or castrated and treated with estradiol implants. APV, CNQX, and bicuculline were included to block fast synaptic transmission. GnRH neurons (47%) expressed a hyperpolarization-activated current with pharmacological and biophysical characteristics ofIh. TheIh-specific blocker ZD7288 reduced hyperpolarization-induced sag and rebound potential, decreased GnRH neuron excitability and action potential firing, and hyperpolarized membrane potential in some cells. ZD7288 also altered the pattern of burst firing and reduced the slope of recovery from the after-hyperpolarization potential. Activation ofIhby hyperpolarization increased spike frequency, whereas inactivation ofIhby depolarization reduced spike frequency. Castration increasedIhcompared with that in gonad-intact males. This effect was reversed byin vivoestradiol replacement. Together, these data indicateIhprovides an excitatory drive in GnRH neurons that contributes to action potential burst firing and that estradiol regulatesIhin these cells. As estradiol is the primary central negative feedback hormone on GnRH neuron firing in males, this provides insight into the mechanisms by which steroid hormones potentially alter the intrinsic properties of GnRH neurons to change their activity.
Testing the Reward Prediction Error Hypothesis with an Axiomatic Model
Authors: Rutledge Robb B. , Dean Mark , Caplin Andrew , Glimcher Paul W.
Published: October 2010

Neuroimaging studies typically identify neural activity correlated with the predictions of highly parameterized models, like the many reward prediction error (RPE) models used to study reinforcement learning. Identified brain areas might encode RPEs or, alternatively, only have activity correlated with RPE model predictions. Here, we use an alternate axiomatic approach rooted in economic theory to formally test the entire class of RPE models on neural data. We show that measurements of human neural activity from the striatum, medial prefrontal cortex, amygdala, and posterior cingulate cortex satisfy necessary and sufficient conditions for the entire class of RPE models. However, activity measured from the anterior insula falsifies the axiomatic model, and therefore no RPE model can account for measured activity. Further analysis suggests the anterior insula might instead encode something related to the salience of an outcome. As cognitive neuroscience matures and models proliferate, formal approaches of this kind that assess entire model classes rather than specific model exemplars may take on increased significance.
Wnts Influence the Timing and Efficiency of Oligodendrocyte Precursor Cell Generation in the Telencephalon
Authors: Langseth Abraham J. , Munji Roeben N. , Choe Youngshik , Huynh Trung , Pozniak Christine D. , Pleasure Samuel J.
Published: October 2010

Oligodendrocyte precursor cells (OPCs) are generated from multiple progenitor domains in the telencephalon in developmental succession from ventral to dorsal. Previous studies showed that Wnt signaling inhibits the differentiation of OPCs into mature oligodendrocytes. Here we explored the hypothesis that Wnt signaling limits the generation of OPCs from neural progenitors during forebrain development. We manipulated Wnt signaling in mouse neural progenitor cultures and found that Wnt signaling influences progenitors cell autonomously to alter the production of OPCs, and that endogenous Wnt signaling in these cultures limits the efficiency of generating OPCs from neural progenitors. To examine these eventsin vivo, we electroporated a soluble Wnt inhibitor or a dominant-negative transcriptional regulator into embryonic mouse neocortical ventricular zone before the usual onset of OPC production and showed that decreasing Wnt signaling in cortical progenitors results in early production of OPCs. Our studies indicate that Wnt signaling influences the timing and extent of OPC production in the developing telencephalon.
Ca2+-Dependent Desensitization of TRPV2 Channels Is Mediated by Hydrolysis of Phosphatidylinositol 4,5-Bisphosphate
Authors: Mercado Jose , Gordon-Shaag Ariela , Zagotta William N. , Gordon Sharona E.
Published: October 2010

TRPV2 is a member of the transient receptor potential family of ion channels involved in chemical and thermal pain transduction. Unlike the related TRPV1 channel, TRPV2 does not appear to bind either calmodulin or ATP in its N-terminal ankyrin repeat domain. In addition, it does not contain a calmodulin-binding site in the distal C-terminal region, as has been proposed for TRPV1. We have found that TRPV2 channels transiently expressed in F-11 cells undergo Ca2+-dependent desensitization, similar to the other TRPVs, suggesting that the mechanism of desensitization may be conserved in the subfamily of TRPV channels. TRPV2 desensitization was not altered in whole-cell recordings in the presence of calmodulin inhibitors or on coexpression of mutant calmodulin but was sensitive to changes in membrane phosphatidylinositol 4,5-bisphosphate (PIP2), suggesting a role of membrane PIP2in TRPV2 desensitization. Simultaneous confocal imaging and electrophysiological recording of cells expressing TRPV2 and a fluorescent PIP2-binding probe demonstrated that TRPV2 desensitization was concomitant with depletion of PIP2. We conclude that the decrease in PIP2levels on channel activation underlies a major component of Ca2+-dependent desensitization of TRPV2 and may play a similar role in other TRP channels.
Generation of Black-Dominant Responses in V1 Cortex
Authors: Xing Dajun , Yeh Chun-I , Shapley Robert M.
Published: October 2010

Consistent with human perceptual data, we found many more black-dominant than white-dominant responses in layer 2/3 neurons of the macaque primary visual cortex (V1). Seeking the mechanism of this black dominance of layer 2/3 neurons, we measured the laminar pattern of population responses (multiunit activity and local field potential) and found that a small preference for black is observable in early responses in layer 4Cβ, the parvocellular-input layer, but not in the magnocellular-input layer 4Cα. Surprisingly, further analysis of the dynamics of black-white responses in layers 4Cβ and 2/3 suggested that black-dominant responses in layer 2/3 were not generated simply because of the weak black-dominant inputs from 4Cβ. Instead, our results indicated the neural circuitry in V1 is wired with a preference to strengthen black responses. We hypothesize that this selective wiring could be due to (1) feedforward connectivity from black-dominant neurons in layer 4C to cells in layer 2/3 or (2) recurrent interactions between black-dominant neurons in layer 2/3, or a combination of both.