Publications by authors named "Anushka Nagpal"

This paper presents room temperature nanoseconds to milliseconds time-resolved spectra and kinetics of the intermediate states and species of bovine and carp fish rhodopsin visual pigments, which also contained ~5% cone pigments. The nanoseconds to milliseconds range cover all the major intermediates in the visual phototransduction process except the formation of bathorhodopsin intermediate which occurs at the femtosecond time scale. The dynamics of these visual pigment intermediates are initiated by excitation with a 532 nm nanosecond laser pulse.

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In this report, we describe the design, construction, and operation of a cell-phone-based Raman and emission spectral detector, which when coupled to a diffraction grating and cell-phone camera system provides means for the detection, recording, and identification of chemicals, drugs, and biological molecules, in situ by means of their Raman and fluorescence spectra. The newly constructed cell-phone spectrometer system was used to record Raman spectra from various chemicals and biological molecules including the resonance enhanced Raman spectra of carrots and bacteria. In addition, we present the quantitative analysis of alcohol-water Raman spectra, performed using our cell-phone spectrometer.

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The resonance Raman spectra of bacterial carotenoids have been employed to identify bacterial strains and their intensity changes as a function of ultraviolet (UV) radiation dose have been used to differentiate between live and dead bacteria. In addition, the resonance-enhanced Raman spectra enabled us to detect bacteria in water at much lower concentrations (∼10 cells/mL) than normally detected spectroscopically. A handheld spectrometer capable of recording resonance Raman spectra in situ was designed, constructed, and was used to record the spectra.

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In this study, absorption, fluorescence, synchronous fluorescence, and Raman spectra of nonirradiated and ultraviolet (UV)-irradiated thymine solutions were recorded in order to detect thymine dimer formation. The thymine dimer formation, as a function of irradiation dose, was determined by Raman spectroscopy. In addition, the formation of a mutagenic (6-4) photoproduct was identified by its synchronous fluorescence spectrum.

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We have designed, constructed, and utilized a charge-coupled device system, integrated with a small Newtonian telescope, capable of long distance recording of bacterial fluorescence and synchronous spectra for the detection of bacteria, their component molecules, and other species. This newly developed optical system utilizes commercial monochrome cameras that we have used to detect various bacterial strains, such as Escherichia coli, and determine their concentrations. In addition, using this system, we were able to differentiate between live and dead bacteria after treatment with ultraviolet light or antibiotics.

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