Spectra Of Water Research Articles

Direct Determination of Tetracycline Hydrochloride and the Interaction with Bovine Serum Albumin by UV Spectra in Water

Direct Determination of Tetracycline Hydrochloride and the Interaction with Bovine Serum Albumin by UV Spectra in Water

Simulation of Broadband Dielectric Spectra of Water and Aqueous Electrolytic Solutions in Terms of the Intermolecular Potential Einartig Representation

Simulation of Broadband Dielectric Spectra of Water and Aqueous Electrolytic Solutions in Terms of the Intermolecular Potential Einartig Representation

Radical Cations of the Monomer and van der Waals Dimer of a Methionine Residue as Prototypes of (2 Center-3 Electron) SN and SS Bonds. Molecular Simulations of Their Absorption Spectra in Water.

Oxidation of peptides or proteins by the OH(•) radicals produced by pulse radiolysis yields species identified by their absorption spectra in the UV-visible domain. However, the case of methionine (Met) in peptides is complex because its oxidation can lead to various free radicals with 2 center-3 electron (2c-3e) bonds. We have performed Monte Carlo/density functional theory molecular simulations of the radical cation of the methylated methionine aminoacid, Met(•+), taken as a model of the methonine residue of peptides, and of the radical cation of its van der Waals dimer, Met2(•+). The cation of the methionine residue displays a 2c-3e SN bond. The cation of dimer Met2(•+) displays three quasidegenerate conformers, one stabilized by a 2c-3e SS bond and the other two stabilized by ion-molecule interactions and made up of a neutral and a cationic unit. These conformers are characterized by their charge and spin density localization and their UV-visible absorption spectra. These spectra enable a discussion of the absorption spectra of the literature; in particular, we emphasize the role of dimers before and after the oxidation process.

Determination of Energy Spectra in Water for 6 MV X Rays from a Medical Linac

Determination of Energy Spectra in Water for 6 MV X Rays from a Medical Linac

Rotation of Water in Solid Parahydrogen and Orthodeuterium

The far-infrared spectra of solid orthodeuterium and solid normal deuterium are presented and compared to the corresponding spectra of solid parahydrogen and solid normal hydrogen. Spectra of water in orthodeuterium are compared to spectra of water in parahydrogen. The water rotation constants in orthodeuterium are approximately 80% of the rotation constants of water in parahydrogen. The S(0)(0) band of orthodeuterium gets a strong satellite in the presence of water. The position and width of the satellite depends on the isotopic composition of the water present. If there is a corresponding satellite in parahydrogen it is weak and closer to the S(0)(0) band of the matrix. The conclusion of the paper is that interaction between guest rotation and the rotation of matrix molecules must be taken into account to explain the reduction of the rotation constants in orthodeuterium.

Pressure Determination by Raman Spectra of Water in Hydrothermal Diamond-Anvil Cell Experiments

Pressure Determination by Raman Spectra of Water in Hydrothermal Diamond-Anvil Cell Experiments

Characteristic Properties Of Attenuated Total Reflection Spectroscopy In Terahertz Region

Experiments on the attenuated total reflection spectroscopy in the terahertz region were carried out using two homemade modules with silicon prisms developed for Fourier spectrometers and a free electron laser as radiation source. Spectra of water, water solutions, perfluorodecaline, paraffine oil, and amino acid powders were recorded. Real and imaging parts of the refractive index were retrieved using Kronig-Kramers transform or by direct solution of Fresnel equations. For a monochromatic radiation source two measurements at two different incident angles, rather than for two polarizations, were found to be an optimal method for the complex refractive index determination.

How to Model Solvation of Peptides? Insights from a Quantum-mechanical and Molecular Dynamics Study of N-Methylacetamide. 1. Geometries, Infrared, and Ultraviolet Spectra in Water

This paper represents the first part of a study of solvation in peptides using quantum-mechanical and classical approaches. In this study, the peptide is modeled as its simplest analogue, namely, N-methyl-acetamide, and the effects of the solvent (here water, and in the second part of the study, water and acetone) are introduced at three different levels, e.g., through a continuum description, using solute-solvent clusters, and using the same clusters embedded in an external continuum. In turn, the solute-solvent clusters have been obtained in two alternative ways, either by using QM optimization procedures or extracting a proper set of structures from MD simulations. In this part of the study, geometries, IR, and UV spectra are calculated in terms of the different solvation models, and the results are analyzed and compared to get insights about different aspects of solvation involving dynamic and static effects on one hand and bulk or specific interactions on the other hand.

Water Spectra in the Region 4200–6250 cm−1, Extended Analysis of ν1+ν2, ν2+ν3, and 3ν2 Bands and Confirmation of Highly Excited States from Flame Spectra and from Atmospheric Long-Path Observations

Water vapor infrared spectra have been recorded at room temperature in the range 4200–6250 cm−1 at resolutions (FWHM) between 0.0053 and 0.0080 cm−1. The use of a White-type multireflection cell made large pressure × pathlength products possible up to 31.27 mbar×288.5 m. The high signal-to-noise ratio allowed us to observe lines with intensities as small as 10−26 cm−1/molecule cm−2 at T=296 K. Among about 5100 recorded water lines, about half of which are reported for the first time, 2351 lines have been assigned to the second triad of H216O (bands ν1+ν2, ν2+ν3, and 3ν2). This has allowed the determination of line positions and corresponding upper rovibrational states with considerably improved accuracy. The assignments of certain highly excited states have been confirmed by the analysis of flame spectra and hot emission spectra. New values of effective Hamiltonian parameters for the upper states {(110), (030), (011)} have been determined. The generating function model was used in the data reduction to account for the anomalously strong centrifugal distortion of the rovibrational levels and resonance interactions. The RMS standard deviation of the least-squares fit of the assigned H2O data was 5×10−3 cm−1 for line positions and 7×10−3 cm−1 for energy levels up to Jmax=20 and Ka(max)=13. Particular attention was paid to water lines in the transparency window 4200–5000 cm−1, in which existing databases are not sufficient. In this region, 1395 lines of four isotopic species of water have been recorded and over 900 accurate line positions of nine bands of H216O (ν1, ν3, 2ν2, ν1+ν2, ν2+ν3, 3ν2, 4ν2−ν2, 2ν2+ν3−ν2, ν1+2ν2−ν2) are reported in this range. A comparison of laboratory spectra with long path atmospheric spectra (20 km slant path in the mountains) in this region shows that many lines missing from available spectroscopic compilations (or considerably shifted compared to observations) are important for a proper interpretation of atmospheric observations. A comparison of the observed data with the best available predictions from the molecular electronic potential energy surface is discussed.

Simulation of broadband dielectric spectra of water and aqueous electrolytic solutions in terms of the intermolecular potential einartig representation.

Simulation of broadband dielectric spectra of water and aqueous electrolytic solutions in terms of the intermolecular potential einartig representation.

Studies on the Effects of Inorganic Ions and their Concentrations on Raman Spectra of Water

Studies on the Effects of Inorganic Ions and their Concentrations on Raman Spectra of Water

Determination of Multiply Scattered Gamma Ray Energy Spectra in Water by the Monte-Carlo Method

The spectral distribution of multiply scattered gamma ray energy in water is determined by the Monte Carlo sampling technique in the energy range 0.5 - 1.6 MeV. It is found that the energy for which the scattered photon number is a maximum, is related to the source energy and this is in agreement with studies made by Minato for a point source in different media.

Spectra of water in the near- and mid-infrared region

Spectra of water have been acquired in the mid-infrared (MIR) and the near-infrared (NIR) region in the temperature range 2–96°C and 4–52°C, respectively. Loading plots from partial-least-squares regression were used to locate isosbestic points in the spectra bands of water. By means of least-squares, the original spectral profiles have been resolved into two spectra, one increasing and the other decreasing with temperature. Concentration profiles of the two structurally different water associations, for the investigated temperature range, were obtained by use of evolutionary curve resolution and first-order differentiation of the MIR spectra. Utilising information from the concentration profiles obtained in the MIR, the NIR spectra were resolved. Relative concentrations were obtained using spectral intensities from the isosbestic points. The complexity in both the fundamental and overtone region of the spectra shows that both structures of water are involved in H-bonding. This result indicates a pseudo-first-order reaction in water, either between an open and a more dense state, or between a rigid, strongly H-bonded state and a more loosely H-bonded state. The cross-correlation pattern between the two regions can be ascribed to the temperature-induced variation in the concentration of the two associations.

Saturation Transfer of Exchangeable Protons in 1H-Decoupled 15N INEPT Spectra in Water. Application to the Measurement of Hydrogen Exchange Rates in Amides and Proteins

Polarization-transfer experiments such as INEPT or DEPT improve the sensitivity of nuclei of low gyro magnetic ratio that are coupled to a nucleus of high gyromagnetic ratio, usually 1H. The INEPT pulse sequence also forms the basis of many two-and three-dimensional heteronuclear NMR experiments. The optimal delay between transients in INEPT is determined by the T1 of the coupled proton. When the nucleus is coupled to a labile proton, however, the efficiency of the experiment is reduced if exchange with solvent protons becomes sufficiently rapid. This aspect can be used to measure the exchange rates of 15N-coupled protons in biomolecules, which, in turn, provides a useful source of structural and dynamic information. In the heteronucleusobserve proton-decoupled INEPT experiment, where all protons are irradiated during acquisition, the intensity of the INEPT signal is determined by the length of the relaxation delay between transients. When the exchange rate of the labile proton is of the order of 1/T1, the rate of recovery is reduced by transfer of saturation from the slowly recovering solvent protons, and the signal intensity at moderate relaxation delays is reduced. A second, faster-exchange regime is entered when the exchange rate of the coupled proton is of the order of J. The contribution of hydrogen exchange to the intensity of the decoupled INEPT signal has been determined by an extension of the theory of saturation transfer developed by Forsén and Hoffman (J. Chem. Phys.40, 1189-1196, 1963). The INEPT experiment has been used to measure the hydrogen exchange rate in a model amide, [15N]acetylglycine, and for several amides in site-selectively labeled M13 coat protein.

Practical Aspects of Recording Multidimensional NMR Spectra in Water with Flat Baselines

Practical Aspects of Recording Multidimensional NMR Spectra in Water with Flat Baselines

Solution conformations of the pituitary opioid peptide dynorphin-(1–13)

Circular dichroism spectra have been measured for dynorphin-(1–13) in water and in solutions of sodium dodecyl sulfate and L-α-lysophosphatidylcholine (palmitoyl). Spectra in water have the features expected for a peptide containing little, if any, order. Small changes are brought about by L-α-lysophosphatidylcholine (palmitoyl), but the resulting spectrum retains the characteristics expected for a random coil. In contrast, sodium dodecyl sulfate produces significant changes which are those expected for induction of α helical content. Quantitative analysis of the circular dichroism spectra suggests the conformation changes from about 5% helix in water to 17% helix in sodium dodecyl sulfate. These results from experiment are in excellent agreement with those obtained from our formulation of the configuration partition function. This formulation predicts a change in helical content from 1% to 19%. The ordering influence is felt most strongly by those residues immediately following the enkephalin sequence.

Effects of Fast-Neutron Irradiation and High-Intensity Magnetic Fields upon Cavitation Thresholds and Nuclei Spectra in Water

The effects of fast-neutron irradiation and a 6-kG magnetic field on the nuclei spectra and cavitation inception thresholds are examined in water. Nuclei spectra are measured using a light scattering technique. An acoustic vibratory horn assembly was used for cavitation generation. It was found that fast-neutron irradiation increased the total number of nuclei above approximately 4 ..mu..m in diameter by approximately 1% and decreased the cavitation inception threshold by approximately 3%. No measurable effect of the magnetic field was found on either nuclei count (and spectrum) or the cavitation threshold.

Human intrinsic factor, isolation by improved conventional methods and properties of the preparation

Intrinsic factor possessing high biological activity was isolated as its cyanocobalamin complex from gastric juice. The purification method consisted of ammonium sulphate precipitations, ion exchange and gel filtration steps and had a yield of about 42%. The vitamin B 12-protein complex was in monomeric form with a molecular weight of approximately 63 000. The amino acid composition resembled that of hog intrinsic factor. Six different carbohydrates were found by gas chromatography, the total content being 8.3%. Spectra in water and alkali indicated that in binding to protein the absorbance of vitamin B 12 was increased over a wide wavelength range. In strong alkali the spectrum approached that of the free vitamin. Accordingly, previous spectrophotometric estimates of the vitamin B 12 content of cyanocobalamin-protein complexes need revision. In isoelectric focusing and gel filtration, no indications were found that the isolated protein differed from that in unfractioned gastric juice.

Fast-Neutron Spectra in Water and Graphite

Fast-Neutron Spectra in Water and Graphite

Some Remarks Concerning the Spectra of Water and Hydroxyl Groups in Beryl

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