bluuebunny/crossref_metadata_2025_split huggingface dataset:
Raman study and lattice dynamics calculation of the misfit layer compound (PbS)1.12VS2
Authors: Sourisseau C. , Cavagnat R. , Fouassier M. , Tirado J. L. , Morales J. 
Published: May 2005

AbstractThe UV—visible (340—800 nm) and Raman spectra (10—900 cm−1) obtained using various laser exciting radiation of a powder sample of the misfit compound (PbS)1.12 VS2 were investigated. In agreement with x‐ray data, vibrational assignments are proposed for most of the internal and external modes of the ‘PBS’ and ‘VS2’ layered sublattices and they were extensively compared with those in the related titanium‐containing compound in order to appreciate the interactions due to the ‘PbS’ donor part of the structure. Owing to the incommensurate structure of (PbS)1.12 VS2, new slightly resonance exhanced Raman signals are detected and they can be explained by the k = O, ± q* selection rules (q* is the modulation vector) as in a previous study of (SnS)1.17 NbS2 and (PbS)1.18 TiS2 compounds. These observations are again confirmed by lattice dynamics calculations which reproduce the essential features of the experimental data and allow one to estimate the strength of interlayer interactions.
Property tensors and tensorial covariants of the 58 magnetic crystallographic point groups
Authors: Brandmüller J. , Illig D. 
Published: May 2005

AbstractAs shown in a previous paper, Neumann's principle allows one to calculate the forms of property tensors and tensorial covariants of classical point groups. A simple extension of this principle permits one to determine also the corresponding expressions for magnetic point groups. In this paper the results for the crystallographic point groups are given.
Determination of enantiomeric excess using Raman optical activity
Authors: Hecht Lutz , Phillips Anthony L. , Barron Laurence D. 
Published: May 2005

AbstractA simple method for the determination of enantiomeric excess is described. It is based on depolarized Raman optical activity (ROA) measurements in right‐angle scattering employing the incident ciruclar polarization (ICP) modulation approach. The accuracy of this method was assessed utilizing α‐pinene as a chiral test compound. The four α‐pinene ICP ROA signals associated with the Raman bands observed at ca. 772, 787, 887 and 929 cm−1 were selected to establish a linear relationship between ROA signal strength and enantiomeric composition for a set of calibration mixtures containing both α‐pinene enantiomers. Using this relationship, a (+)‐α‐pinene sample content of 16.3% was determined for a blind mixture containing 83.6% (1S)‐( — )‐α‐pinene and 16.4% (1R)‐(+)‐α‐pinene. Similary, utilizing additional spectral subtraction procedures, a (+)‐α‐pinene sample content of 1.5% was estimated for a test mixture consisting of 50.1% (1S)‐( — )‐α‐pinene and 49.9% (1S)‐( — )‐trans‐pinane.
Raman tensor of adenine residue for the 1580 cm−1 vibration and its orientation in a biopolymer
Authors: Tsuboi Masamichi , Ueda Toyotoshi , Ushizawa Koichi , Nagashima Nobuya 
Published: May 2005

AbstractThe adenine residues of nucleic acids give a medium‐intensity Raman band around 1580 cm−1 and protonated adenine residue around 1560 cm−1. Each of them shows a peculiarly high degree of depolarization, α = 0.65, in aqueous solutions. A corresponding band, at 1562 cm−1, shows a high anisotropy in the single crystal of uridylyl‐(3′‐5′)‐adenosine (UpA). On the basis of the known structure of this crystal, and on the basis of the polarized Raman data (488.0 nm excitation), the shape and orientation of the Raman tensor associated with this 1562 cm−1 vibration have been determined: one of its principal axes (y‐axis) is directed along the long axis of the adenine residue and r1 = αxx/αzz = − 3 and r2 = αyy/αzz = 4. A general relationship has also been derived between the orientation angles (θ and χ) of the adenine residues with a uniaxial arrangement in a biopolymer and the anisotropy of the 1580 cm−1 Raman scattering intensity. This relationship has been used in a discussion of the orientation of the adenine residue in the poly(rA)·poly(rU) duplex fibre.
Picosecond transient Raman spectra of photoexcited 4‐dimethylamino‐4′‐nitrostilbene in polar solvents
Authors: Nakabayashi T. , Okamoto H. , Tasumi M. 
Published: May 2005

AbstractPicosecond transient Raman spectra of photoexcited 4‐dimethylamino‐4′‐nitrostilbene in polar solvents (acetonitrile, acetone and benzonitrile) were observed and the decay kinetics of the observed Raman bands were analysed. The observed solvent dependences of the peak positions suggest that the transient Raman bands arise from a non‐radiative charge‐transfer (CT) state. Molecules in the vibrationally excited CT states were also observed by monitoring transient anti‐Stokes Raman scattering. These results indicate that a rapid non‐radiative transition occurs from the lowest allowed singlet state to vibrationally excited CT states.
Fourier transform Raman and fourier transform ir spectroscopic investigation of pyrazine adsorbed by sepiolite and bentonite from anatolia
Authors: Akyüz S. , Akyüz T. , Davies J. E. D. , Esmer K. , Özel A. Erbölükbaş 
Published: May 2005

AbstractThe adsorption of pyrazine by two different Anatolian sepiolites and by natural and ion‐exchanged (Fe, Co, Cu and Sn) bentonites was investigated by vibrational spectroscopy. The spectroscopic results indicate that the pyrazine molecules adsorbed on sepiolite and bentonites are coordinated to either surface hydroxyls by H‐bonding interaction (in the case of sepiolite) or to exchangeable cations (in the case of bentonites) through both nitrogen lone pairs as bidentate ligands. X‐ray diffraction patterns of the clays were also recorded and the basal spacings of pyrazine‐treated natural and ion‐exchanged bentonites were found to be around 14.7 Å. The results suggest that pyrazine molecules intercalate the interlayers of bentonite with a monolayer arrangement.
Effect of nafion on geometry and axial ligation in manganese (III) tetraphenylporphyrins
Authors: Maclean Angela L. , Armstrong Robert S. , Kennedy Brendan J. 
Published: May 2005

AbstractManganese(III) porphyrins were successfully incorporated into Nafion, wherein they are located in the ionic pockets of the polymer. The result of UV—visible spectroscopy indicate that at least one solvent molecule and the anion accompany the macrocycle into the membrane. The anion is only loosely associated with the porphyrin, but strongly coordinating solvents such as pyridine remain in the axial coordination sites. Dramatic changes which were observed in the electronic and resonance Raman spectra when THF and dioxane were used as incorporation solvents indicate that the geometry of the macrocyle also changes when in Nafion. Puckering of the porphyrin ring apparently occurs as it interacts with the restrictive environment in Nafion.
Raman spectroscopic study of the avidin—biotin complex
Authors: Fagnano C. , Fini G. , Torreggiani A. 
Published: May 2005

AbstractRaman spectra of avidin, biotin and the avidin‐biotin complex were recorded. The percentages of secondary structure of avidin and the avidin‐biotin complex were obtained from the Raman spectra. The vibrational results indicate that, as a consequence of the interaction of avidin with biotin, the β‐sheet conformation percentage decreases and the α‐helical conformation percentage increases. Moreover, the interaction of avidin with biotin is also able to change slightly the tertiary structure of the protein. In fact, as a consequence of the binding of biotin, the hydrophobicity of the environment of Trp increases slightly according to the intensity increase of the 1360 cm−1 component. The intesity of all bands attributable to Trp residues increases with biotin binding, indicating that Trp is directly involved in the interaction. These results are in agreement with the results of UV measurements which indicate a red shift of the avidin Trp absorption bands as a consequence of the binding to biotin.
Vibrational study of eight‐membered titanium and germanium‐containing siloxane rings
Authors: Haoudi‐Mazzah A. , Dhamelincourt P. , Gnado J. , Mazzah Ahmed 
Published: May 2005

AbstractBy a condensation reaction of tBu2Si(OH)2(L) with titanium and germanium tetrahalides several eight‐membered titanium and germanium cyclosiloxane compounds were prepared in polar solvents. These were crystallized and identified by the usual physical techniques (1H, 13C and 29Si NMR spectroscopy, x‐ray diffraction and mass spectrometry). Raman and IR spectra were also recorded, which confirmed the structure obtained by x‐ray diffraction. The rings are well characterized by breathing modes which appear around 620–660 cm−1 and Si‐O‐M stretching‐bending modes which appear around 950–1000 cm−1. The vibrational modes characterizing the tert‐ butyl group are weakly coupled with those of the heterocycles. The corresponding observed bands are close to those observed for (L).
Conformational equilibria for 3‐methylstyrene: Raman and FTIR spectra and ab initio calculations
Authors: Meurisse I. , Ribeiro‐Claro P. J. A. , Teixeira‐Dias J. J. C. , Pouchan C. 
Published: May 2005

AbstractThe Raman spectra of liquid 3‐methylstyrene show pairs of bands whose temperature‐dependent intensities clearly suggest the occurrence of a conformational equilibrium. From these bands, assigned to cis and trans conformers, a trans‐cis energy difference of 0.8 + 0.2 kJ mol−1 was obtained for the liquid phase. On the other hand, ab initio calculations at the 3‐21G** and MP2/3‐21G* levels predict a cis form more stable than the trans form by less than 0.15 kJ mol−1, in good agreement with gas‐phase literature results.
Raman scattering investigation of the central peak in lead lanthanum zirconate—titanate‐x/95/5 ceramics with × = 0—4 mol% of La2O3
Authors: El‐Harrad I. , Becker P. , Carabatos‐Nédelec C. , Handerek J. , Ujma Z. , Dmytrow D. 
Published: May 2005

AbstractIt is demonstrated that in the ferroelectric phase of the PLZT‐x/95/5 ceramics the spontaneous polarization is the order parameter, the fluctuations of which are mainly responsible for the dielectric relaxations manifested in the Raman spectra by the appearance and the evolution of a central peak. For T >315°C, in the paraelectric phase, the spontaneous polarization fluctuations are substituted by the fluctuations of the appearing local concentration polarization. Above the Curie temperature, the thermally activated relaxation process gives an activation energy of 0.7 eV.
New method for obtaining Raman spectra of extremely small quantities of light‐absorbing substances adsorbed on silver from very dilute solutions
Authors: Macklin John W. 
Published: May 2005

AbstractMicro‐Raman spectra of picogram to sub‐femtogram quantities of several chromophoric substances adsorbed from dilute solution on silver were measured and compared with similar measurements on some non‐chromophoric substances. The silver surface enhanced resonance Raman measurements require no redox roughening of the surface, sometimes no applied potential and only 1‐2 mW of defocused laser power. The new method by which silver surface enchancement is achieved requires contact of the surface with halide ion solution for several hours. The most astounding results thus far were achieved with 1, 1′‐diethyl‐2,2′‐cyanine iodide (2,2′‐cyanine). Raman spectra of the adsorbate from 20 ml of 1 × 10−17 M solution of the dye were measured using the method. Further characteristics of the phenomenon were obtained based on extensive Raman measurements on 2,2′‐cyanine. Some further details resulting from these measurements are described.
A comparative study of eggshell proteins in lepidoptera
Authors: Paul Miles , Kafatos Fotis C. , Regier Jerome C. 
Published: May 2005

AbstractAs a first step in the study of chorion composition, biochemical development and morphogenesis, we have studied the proteins of moth chorions (eggshells). We draw attention to the extensive similarities of these proteins in a variety of species. We also report that the eggshell proteins are deposited in succession, each with its characteristic time table. This phenomenon may be related to the morphogenesis of chorion.
Mitochondrial membranes and mutagenesis by ethidium bromide
Authors: Mahler Henry R. , Perlman Philip S. 
Published: May 2005

AbstractThe conversion of wild type (ρ+) to cytoplasmic petites (ρ−) in Saccharomyces cerevisiae, à mutation in mitochondrial DNA, can be brought about with high efficiency by low concentrations of ethidium bromide (EB). The rate and extent of mutagenesis and its expression can be influenced, and even reversed, by a number of genetic lesions, agents or treatments affecting mitochondrial structure and metabolism. Among them are incubation at 45°, exposure to Antimycin A, growth on different carbon sources and the presence or absence of 2 different gene products previously implicated in the repair of UV induced lesions in mitochondrial DNA. Based on these observations a model for EB mutagenesis is advanced which postulates a complex between mitochondrial DNA and the inner membrane as the target susceptible to modification by EB. This model predicts that altered membranes should lead to changes in the susceptibility of cells to the mutagenic action of EB. This prediction has been verified by comparing cells that contain one of 2 structurally quite distinct monounsaturated C18 fatty acids in their mitochondrial phospholipids: greater resistance to mutagenesis and ease of thermal protection is exhibited when cells – and mitochondria – contain oleic (Δ9cis, m.p. < 5°) rather than petroselinic (Δ6cis, m.p. 28°) acid in their phospholipids. As a corollary, studies on EB mutagenesis and mitochondrial DNA may be used as probes for the mitochondrial inner membrane to reveal some perhaps novel functions.
The effects of branched chain fatty acid incorporation into Neurospora crassa membranes
Authors: Brody Stuart , Allen Barry 
Published: May 2005

AbstractPhytanic acid (3,7,11,15‐tetramethylhexadecanoic acid), an unusual branched chain fatty acid thought to disrupt the hydrophobic regions of membranes, can be incorporated into the lipids of growing Neurospora cultures. The phytanic acid must be supplied in a water soluble form, esterified to a Tween detergent (Tween‐Phytanic). This fatty acid and its oxidation product, pristanic acid, were found in both the phospholipid and neutral lipid fractions of Neurospora. In phospholipids of the wild‐type strain, phytanic acid was present to the extent of 4 to 5 moles percent of the fatty acids and pristanic acid, about 41 moles percent. The neutral lipids contained 42 and 4 moles percent of phytanic and pristanic acids respectively. By employing a fatty acid‐requiring mutant strain (cel−), the phytanic acid level was raised to a maximum of 16 moles percent in the phospholipids and to 63 moles percent in the neutral lipids. Under this condition, the level of pristanic acid was reduced to about 6 moles percent in phospholipids and 1 mole percent in the neutral lipids. The phytanic acid levels could not be further elevated by increased supplementation with phytanic acid or by a change in the growth temperature. In strains with a high phytanic acid content, the complete fatty acid distribution of the phospholipids and neutral lipids was determined. In the neutral lipids, phytanic acid appeared to replace the 18 carbon fatty acids, particularly linoleic acid.The presence of phytanic acid in the phospholipids was confirmed by mass spectrometry, and by the isolation of a phospholipid fraction containing this fatty acid via silicic acid column chromatography. Most of the phytanic acid in phospholipids appeared to be in phosphatidylethanolamine, and 2 lines of evidence suggest that it was esterified to both positions of this molecule. In the fatty acid‐requiring mutant strain (cel−), the replacement by phytanic acid of 10 to 15% of the fatty acids in the phospholipid produced an aberrant morphological change in the growth pattern of Neurospora and caused this organism to be osmotically more fragile than the wild‐type strain. The lack of noticeable effect of the high levels of pristanic acid in the phospholipids suggests that it is not just the presence of the methyl groups in a branched chain fatty acid which leads to the altered membrane function in this organism.
The kinetics of colicin E3 induced fragmentation of Escherichia coli 16S ribosomal RNA in vivo
Authors: Samson A. C. R. , Senior B. W. , Holland I. B. 
Published: May 2005

AbstractFixation of colicin E3 to sensitive bacteria is followed, after a lag of 2 to 6 min, by the rapid degradation of all the RNA of the 30S ribosomal subunits, yielding a large 15.5S fragment and a smaller fragment, containing the 3′‐terminal end of the 16S RNA. The small RNA fragment which was estimated to consist of about 52 nucleotides, was retained within the 30S subunit in vivo and was subsequently recovered quantitatively without apparent further degradation. Kinetic studies of the cleavage of 16S RNA indicated that this is the primary and lethal effect of colicin E3 and the primary cause of the observed inhibition of protein synthesis in vivo. Small amounts of an RNA fragment, apparently identical in size to the small E3‐fragment, were also isolated from 30S particles obtained from untreated bacteria.
Studies on mixed micelles of triton X–100 and phosphatidylcholine using nuclear magnetic resonance techniques
Authors: Dennis Edward A. , Owens Jerry M. 
Published: May 2005

AbstractThe addition of the nonionic detergent Triton X‐100 to aqueous phosphatidyl‐choline dispersions converts the bilayer structures to mixed micellar structures containing Triton X‐100. High‐resolution nuclear magnetic resonance spectroscopy at 220 MHz was used to follow this conversion, and the general spectral characteristics of the mixed micelles are presented. The results are discussed in terms of the precise change in structure which occurs as Triton is mixed with the phospholipid bilayers, and it is concluded that, above a molar ratio of about 2:1 Triton to phospholipid, most or all of the phospholipid is in mixed micelles. The relevance of these results to the study of enzymes which require substrate in the form of micelles is discussed.
Structural studies on the organization of proteins in mitochondrial membranes using proteolytic enzymes
Authors: Pasquali Petronio , Landi Laura , Masotti Lanfranco , Lenaz Giorgio 
Published: May 2005

AbstractProteolytic enzymes, pronase and trypsin, digest protein in ETP and in SU‐particles (devoid of the soluble ATPase) at similar rates and to the same extents for intact and lipid‐depleted membranes, showing that lipids do not constitute a barrier to the action of the proteases. The rates and extents of hydrolysis are slightly depressed when membranes are reconstituted from lipid‐depleted particles and phospholipids. The hydrolysis rates for the various particles are not greatly enhanced by detergent solubilization nor by other denaturing treatments, indicating that the rates measured in absence of treatments are maximal under the conditions used. The circular dichroism spectra of pronase treated ETP are noticeably altered showing modification of the original conformation. Moreover, enzymic activities of mitochondria and submitochondrial particles are progressively affected by proteases according to their localization at, or near to, a given surface of the membrane. The matrix enzyme, malate dehydrogenase, is not apparently released from mitochondria during the initial incubation period. The results are tentatively discussed in terms of organization of lipids and proteins in the mitochondrial membrane.
Colicin Ia and Ib binding to Escherichia coli envelopes and partially purified cell walls
Authors: Konisky Jordan , Cowell Billie S. , Gilchrist Mary J. 
Published: May 2005

AbstractThe specific binding of 125 Iodine labelled colicin Ia and Ib to Escherichia coli cell envelopes and partially purified cell walls is demonstrated. Neither partially purified cytoplasmic membranes isolated from a wild type sensitive strain nor envelopes or cell walls prepared from an E. coli mutant known to be defective in the colicin I receptor could bind the colicins. Competition studies suggest that colicins Ia and Ib have a common bacterial receptor which resides in the bacterial cell wall.
Selective solubilization of proteins from red blood cell membranes by protein perturbants
Authors: Steck Theodore L. , Yu John 
Published: May 2005

AbstractIsolated human erythrocyte membranes were exposed to a series of reagents known to modify or perturb proteins; these included sodium hydroxide, lithium diiodosalicylate, acid anhydrides, and organic mercurials. Each reagent liberated the same set of relatively polar polypeptides from the membrane, while the other, more hydrophobic species invariably remained associated with the membrane residue. The selective elution pattern was precisely that seen previously with 6 M guanidine hydrocloride. The released polypeptides, comprising half of the membrane protein mass, contained no carbohydrate; current evidence indicates that all of these components are confined to the cytoplasmic surface of the membrane. The residue contained all the lipids and all the glycoproteins. The latter are accessible to the outer membrane surface and, in at least two cases, seem to extend asymmetrically across the thickness of the membrane. Thus, the distinctive elution behavior which defines these two groups of polypeptides relates both to their chemical composition and their organizational disposition in the membrane.
Lateral diffusion of rhodopsin in the visual receptor membrane
Authors: Poo Mu‐ming , Cone Richard A. 
Published: May 2005

AbstractIf the rhodopsin on one side of an isolated rod outer segment is suddenly bleached, the rhodopsin on the other side can be observed with a microspectrophotometer to diffuse rapidly across the width of the rod. Uniform distribution is approached exponentially with a half‐time at 20°C of 23 ± 3 sec in rods isolated from mudpuppy (Necturus maculosus) retina and 35 ± 3 sec in rods isolated from frog (Rana catesbeiana) retina. These rods are 12 and 8 μ in diameter, respectively. Taking the geometry of the rod disk membranes into account, we obtain a lateral diffusion constant for rhodopsin in the disk membrane of (4.0 ± 1.5) × 10−9 cm2/sec for both mudpuppy and frog. No diffusion was observed if rods were first fixed with glutaraldehyde. The diffusion constant increased with temperature with a Q10 between 2 and 4 in the temperature range near 20°C. If the effective diameter of rhodopsin is assumed to be about 50 Å, the Stokes–Einstein relationship implies the effective viscosity for lateral diffusion of rhodopsin is about 2 poise. This value, as well as the Q10, are essentially the same as indicated by the rapid rotational diffusion of rhodopsin previously observed by flash photometry in frog rods.Cone, R. A., Rotational Diffusion of Rhodopsin in the Visual Receptor Membrane, Nature (London) New Biology, 236:39 (1972).