Biomedical subjects

D Bruce Chase

Publications and source records attributed to D Bruce Chase.

7 recordsLinked to original sources

PubMed2005

New developments in planar array infrared spectroscopy.

A planar array infrared (PA-IR) spectrograph offers several advantages over other infrared approaches, including high acquisition rate and sensitivity. However, it suffers from some important drawbacks, such as a limited spectral range and a significant curvature of the recorded spectral images, which still need to be addressed. In this article, we present new developments in PA-IR spectroscopy that overcome these drawbacks. First, a data processing method for the correction of the curvature observed in the spectral images has been developed and refined. In addition, a dual-beam instrument that allows the simultaneous recording of two independent spectral images has been developed. These two improvements have been combined to demonstrate the real-time background correction capability of PA-IR instruments. Finally, the accessible spectral range of the PA-IR spectrograph has been extended to cover simultaneously the methylene stretching (3200-2800 cm(-1)) and the finger-print (2000-1000 cm(-1)) spectral regions.

Algorithms↗

PubMed2004

Acquisition of mid-infrared spectra from nonrepeatable events with sub-100-micros temporal resolution using planar array infrared spectroscopy.

A novel method is presented that is capable of collecting time-resolved vibrational spectroscopic information with sub-100-micros temporal resolution. Unlike previous step scan FT-IR approaches, the phenomena under study do not necessarily need to be repeatable. The methodology described herein is based on the planar array infrared (PA-IR) technique, which utilizes a spectrograph for wavelength dispersion and a mid-infrared focal plane array (FPA) detector for simultaneous detection of multiple wavelengths. Unlike previous PA-IR approaches, a rolling mode FPA is employed. This unique data readout mode, where data are read out of the array two rows at a time, is exploited to generate increased temporal resolution. The capabilities of this technique are demonstrated using the example of the electric field-induced Freedericksz transition of a nematic liquid crystal. It is shown that the orientational dynamics of a single transition can be tracked over a spectral range of 154 cm(-)(1) with a temporal resolution of 99.17 micros while requiring a total experimental time of less than 1 s.

Journal Article↗

PubMed2004

Time-resolved IR studies of monolayer self-assembly on a gold substrate using planar array infrared (PA-IR) spectroscopy.

Time-resolved and spatially resolved infrared spectra (line images) of self-assembled monolayers of octadecylthiol (ODT) on gold substrates were investigated by planar array infrared (PA-IR) spectroscopy, with a grazing incidence reflection attachment. It was observed that PA-IR spectra with a good signal-to-noise ratio that is comparable to those obtained from Fourier transform infrared spectroscopy could be acquired with a significantly shorter collection time. Focusing on the peak intensities and peak positions of the CH2 asymmetric stretch (approximately 2918 cm(-1)) and the CH3 symmetric stretch (approximately 2960 cm(-1)), respectively, the molecular orientation and organization of the monolayers were determined. The ODT formed a uniform monolayer on the surface of the gold whether it was deposited within 1-2 s or over a 40 h period. Disordered monolayers formed instantly, and with an increase in dipping time, the monolayer became more ordered, becoming highly ordered after dipping times of many ( > 24) hours.

Journal Article↗

PubMed2004

A faster approach to infrared rheo-optics using a planar array infrared spectrograph.

Infrared rheo-optics combines dynamic mechanical analysis with infrared spectroscopy to provide molecular level information about the segmental reorientation and the changes in local environment associated with the dynamic deformation of polymers. Up to now, the application of this technique has been limited by the amount of time necessary to perform the experiments. In this article, we demonstrate that the use of a planar array infrared (PA-IR) spectrograph can accelerate the acquisition time by as much as two orders of magnitude while maintaining a signal-to-noise ratio (SNR) similar to that obtained using step-scan Fourier transform infrared (FT-IR) spectrometry, and by more than three orders of magnitude at the expense of a reduced SNR. The advantages and drawbacks of this new technique are discussed.

Elasticity↗

PubMed2004

Near-field infrared imaging and spectroscopy of a thin film polystyrene/poly(ethyl acrylate) blend.

The application of broadband, near-field infrared microscopy to the characterization of the mesoscale structure of a thin film polymer blend is described. Key features of this instrument, which couples the nanoscale spatial resolution of scanning probe microscopy with the chemical specificity of vibrational spectroscopy, include broad tunability and bandwidth, parallel spectral detection for high image acquisition rates, and infrared-transparent aperture probes. Nearfield spectral transmission images of a thin film of polystyrene/poly(ethyl acrylate) acquired in the C-H stretching region are reported. An assessment of the relative importance of transmission image contrast mechanisms is a significant aim of this work. Analysis of the near-field infrared spectra indicates that the image contrast in the C-H stretching region is largely due to near-field coupling and/or scattering effects. Identification and differentiation of the operative contrast mechanisms on the basis of their relative dependence on wavelength is discussed. Analysis of the contrast attributed to absorption is consistent with the chemical morphology of this sample derived from previous chemical modification/atomic force microscopy studies.

Journal Article↗

PubMed2004

Performance and application of a new planar array infrared spectrograph operating in the mid-infrared (2000-975 cm(-1)) fingerprint region.

A no-moving-part planar array infrared spectrograph (PA-IR) equipped with a 256 x 256 mercury cadmium telluride (MCT) focal plane array has been designed and constructed. The performance of the instrument, whose frequency range extends from 2000-975 cm(-1), has been assessed in terms of resolution, bandwidth, and signal-to-noise ratio. The PA-IR spectrograph is able to record spectra with an 8.7 ms time resolution and has peak-to-peak noise levels as low as 2.4 x 10(-4) A.U. As a demonstration of the potential of PA-IR, the dynamics of reorientation of a liquid crystalline sample exposed to a single electric field pulse has been studied. It was shown that PA-IR can be used for the simultaneous acquisition of two orthogonally polarized spectra. The advantages and limitations of PA-IR, step-scan Fourier transform infrared (FT-IR), and ultrarapid-scanning FT-IR for real-time studies of reversible and irreversible phenomena are thoroughly discussed.

Polymers↗

PubMedDate not supplied

Effects of electrospinning and solution casting protocols on the secondary structure of a genetically engineered dragline spider silk analogue investigated via Fourier transform Raman spectroscopy.

Micrometer and submicrometer diameter fibers of recombinant dragline spider silk analogues, synthesized via protein engineering strategies, have been electrospun from 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) and compared with cast films via Raman spectroscopy in order to assess changes in protein conformation that may result from the electrospinning process. Although the solvent casting process was shown to result in predominantly beta-sheet conformation similar to that observed in the bulk, the electrospinning process causes a major change in conformation from beta-sheet to alpha-helix. A possible mechanism involving electric field-induced stabilization of alpha-helical segments in HFIP solution during the electrospinning process is discussed.

Amino Acid Sequence↗