bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Raman spectrum of brookite, TiO2 (Pbca, Z = 8)
Authors: Tompsett G. A. , Bowmaker G. A. , Cooney R. P. , Metson J. B. , Rodgers K. A. , Seakins J. M. 
Published: May 2005

AbstractThe Raman microprobe spectra of natural brookite crystals from Switzerland and Brazil and a synthetic brookite powder exhibit a characteristic intense band at 153 cm−1. In contrast, anatase has a band of similar intensity at 144 cm−1 and rutile lacks a strong band in this region. Polarization experiments with the Brazilian crystal permit 17 out of a predicted 36 vibrational bands to be readily assigned as A1g (127, 154, 194, 247, 412, 640 cm−1), B1g (133, 159, 215, 320, 415, 502 cm−1), B2g (366, 395, 463, 584 cm−1) and B3g (452 cm−1). Eight weaker bands and component sub‐bands resolved at 172, 287, 545, 618 cm−1, 254, 329, 476 cm−1 and 497 cm−1 are tentatively assigned to B3g, B2g and A1g modes respectively. Traces of Si and Fe in the Brazilian crystal and Si, Fe, Al and S in the Swiss sample are indicated by spot electron microprobe analysis. Electron spin resonance spectra suggest small amounts of Fe3+ are substituting for Ti4+ in the structure. Concomitant protonation of oxygens to maintain charge balance yields OH groups which give rise to three sharp, low‐intensity absorption bands near 3360, 3380 and 3404 cm−1 in the infrared spectra. X‐ray photoelectron spectroscopy shows that surface‐bound OH/H2O species exist in both crystals but no detectable Ti3+.
Vibrational study of diglycolic acid and potassium diglycolate salts
Authors: Ramsis H. , Perez‐Ruiz E. , Roger J. , Bourret E. , Delarbre J. L. , Maury L. 
Published: May 2005

AbstractThe Raman and infrared spectra of diglycolic acid and its potassium salts in aqueous solution were recorded from 4000 to 200 cm−1. Vibrational assignments were made for all the observed wavenumbers on the basis of isotopic wavenumber shift, depolarization ratios and group wavenumber considerations and comparison with accepted assignments for certain vibrational modes in other similar compounds. The three compounds (the acid, the acid salt and the neutral salt) belong to the Cs symmetry group, but their conformations are quite different. In the crystalline state, the acid salt has a strong hydrogen bond and appeared to be of type A according to Speakmann's classification.
Polarization‐sensitive resonance CSRS of deoxy‐and oxyhaemoglobin
Authors: Voroshilov Artemy , Lucassen Gerald W. , Otto Cees , Greve Jan 
Published: May 2005

AbstractPolarization‐sensitive coherent Stokes Raman scattering (CSRS) measurements of oxy‐ and deoxyhaemoglobin in aqueous solutions are reported. The excitation wavelengths used were chosen in the region of the Q absorption bands to achieve twofold electronic resonance. The dispersion profiles of all independent susceptibility χ(3) components and purely anisotropic and anti‐symmetric scattering contributions were resolved within the frequency non‐degenerate CSRS scheme. Eight bands of oxyhaemoglobin and five bands of deoxyhaemoglobin were observed in the range 1500‐1680 cm−1. Simultaneously fitting sets of polarization spectra provided vibrational parameters (positions, bandwidths, amplitudes, phases and CSRS depolarization ratios) for each compound. Major bands were assigned to the non‐totally symmetric v10, v11 and v19 modes of the porphyrin macrocycle. The phases calculated exhibited a correlation with the symmetry of the vibrations. On the basis of the spectral fits, the three additional peaks arising in the oxyhaemoglobin spectra could be ascribed to the bands of intermediate deoxyhaemoglobin. The occurrence is due to the partial photolysis of oxyhaemoglobin. Vibrational parameters of these bands were found to be essentially similar to the parameters of the bands observed in the spectra of the stable deoxyhaemoglobin. Despite the asymmetric character predicted, the major bands were all contributed to by a considerable isotropic component. A decrease in the depolarization ratio P of the anomalously polarized v19 mode from 7.7 in oxyhaemoglobin to 4.3 in deoxyhaemoglobin was observed. Such a decrease in anti‐symmetric character of the vibration on release of the ligand supports the occurrence of deformation of the haem ring system.
High‐pressure Raman study of SrMoO4 up to 37 GPa and pressure‐induced phase transitions
Authors: Jayaraman A. , Wang S. Y. , Shieh S. R. , Sharma S. K. , Ming L. C. 
Published: May 2005

AbstractPressure‐induced phase changes in SrMoO4 were investigated by high‐pressure Raman spectroscopy in a diamond anvil cell. The scheelite‐type SrMoO4 transforms in to a monoclinic lattice near 13 GPa and retains this structure up to 37 GPa, the limit of pressure tested. There is no pressure‐induced amorphization in this simple molybdate up to this pressure, as in the case of structurally complex molybdate systems. The optical absorption characteristics of SrMoO4 change considerably with pressure, the sample turning progressively deep orange‐brown with increase in pressure. This change is connected with the lowering of the d‐state of molybdenum in the MoO4 ion with increase in pressure.
Dual circular polarization Raman optical activity of related terpene molecules: Comparison of backscattering DCPI and right‐angle ICP spectra
Authors: Yu Gu‐Sheng , Freedman Teresa B. , Nafie Laurence A. 
Published: May 2005

AbstractThe backscattering in‐phase dual circular polarization (DCPI) Raman and Raman optical activity (ROA) for a series of terpene molecules is reported. The selected molecules were studied in three groups of closely related structures and correlations between ROA features and structural elements among molecules within these groups are discussed. One aim of this study was to uncover additional details regarding the sensitivity of ROA to stereostructural features in molecules and to elucidate further the degree of local character of this new stereochemical probe. Another was to compare the backscattering DCPI ROA intensities reported here with those obtained using depolarized right‐angle incident circularly polarized (ICP) ROA for some of the same molecules more than a decade ago.
UV‐excited continuum resonance Raman scattering from 35Cl2
Authors: Vogt P. , Schmitt M. , Kiefer W. 
Published: May 2005

AbstractHigh‐resolution Raman spectra of isotopically pure 35Cl2 were recorded using UV argon ion laser radiation of 275.4, 300.3, 302.4 and 305.5 nm. Overtone progressions could be observed for excitation with 300.3, 302.4 and 305.5 nm radiation. All overtone transitions could be simulated satisfactorily using both the traditional Kramers‐Heisenberg‐Dirac equation and time‐dependent quantum theory. The results obtained for 35Cl2 are compared to those derived earlier for I2 and Br2. The spectral features of the fundamental band for excitation in the UV region can be explained by assuming a destructive interference effect between resonant and non‐resonant Raman scattering resulting from adjacent high‐energy electronic states.
Fourier transform Raman spectroscopic study of fungi
Authors: Edwards H. G. M. , Russell N. C. , Weinstein R. , Wynn‐Williams D. D. 
Published: May 2005

AbstractFourier transform (FT) Raman spectra of the cell walls of three species of fungi are reported for the first time, namely (i) Agaricus bisporus, a fruiting bud, (ii) Mortierella genus and (iii) Mucor genus. Some molecular assignments are proposed for the major vibrational features and attributed to chitin, N‐acetylglucosamine and (R)‐glucan. Preliminary studies indicate that it is possible to use FT‐Raman spectroscopy to discriminate between different mixed species in culture media.
Low‐temperature polarized single‐crystal Raman spectra of the β‐alums CSM(SO4)2. 12H2O (M = Mo or Ru) between 275 and 1200 cm−1
Authors: Armstrong Robert S. , Beattie James K. , Best Stephen P. , Cole Bradley D. , Tregenna‐Piggott Philip L. W. 
Published: May 2005

AbstractLow‐temperature, polarized, single‐crystal Raman spectra of the β‐alums CsM(SO4)2. 12H2O (M = Mo or Ru) and their deuterated analogues were recorded between 275 and 1200 cm−1. The internal modes of sulphate and [M(OH2)6]3+and the external modes of water coordinated to the mono‐ and tervalent cation were assigned. This allowed a comparison between the wavenumbers of the internal modes of second‐ and first‐row transition metal hexaaquacations. The relationship betweenv1(MO6) and the MIII—O bond length is similar for the first‐row transition and Group 13 metals, but is significantly different for the second‐row transition metals. This suggests a non‐ionic contribution to the metal‐water bonding in the latter case. The relative intensities of thev1(MO6) modes are highly dependent on the identity of the metal; however, the trend in this property is not simply related to either the bond strength, the polarizing power of the cation or the covalent interaction.
Small‐angle X‐ray scattering of human serum high‐density lipoproteins
Authors: Shipley G. G. , Atkinson D. , Scanu A. M. 
Published: May 2005

AbstractSmall‐angle x‐ray scattering (SAXRS) studies of the human serum high‐density lipoprotein HDL2 indicate a symmetrical particle with a radius of gyration Rg = 46 Å. The positions and intensities of subsidiary maxima in the scattering curves are not consistent with those of a uniformly electron dense sphere. Scattering curves calculated for spheres with a step‐model radial electron density distribution, show good agreement with the experimental scattering curve for HDL2 only for specific values of the step function used. The dimensions obtained for the electron‐deficient core and electron‐rich shell model are quantitatively consistent with a predominantly surface location for the HDL2 protein and phospholipid head groups, the more hydrocarbon species being located in the interior of the particle.
Lipid–protein and lipid–lipid interactions in cytochrome oxidase model membranes
Authors: Jost Patricia C. , Capadil Roderick A. , Vanderkooi Garret , Griffith O. Hayes 
Published: May 2005

AbstractTwo lipid environments are detected in membranous cytochrome oxidase, using spin labeling techniques. This model membrane system consists of closed vesicular membranes formed spontaneously when the membrane protein is isolated with its accompanying phospholipids. The data show both an immobilized component, which is constant in amount, and a fluid component. Based on spectral analysis, the interpretation is that the bound component represents a single layer of lipid immobilized on the surface of the protein between the hydrophobic protein complex and the adjacent fluid bilayer regions. Maximal enzyme activity of this functional protein complex is attained when all of the bound sites are occupied, and above this level additional phospholipid (bilayer) has little or no effect on the enzyme activity.
Lateral phase separations in membranes
Authors: Shimshick E. J. , Kleemann W. , Hubbell W. L. , McConnell H. M. 
Published: May 2005

AbstractLateral phase separations of phospholipids in both bacterial membranes and model membrane systems (phospholipid bilayers) can be studied using spin labels. Temperature–composition phase diagrams have been determined for binary mixtures of lipids dispersed in excess water by measurements of changes in the fluidity of the membranes as a function of temperature. These results have been used to interpret similar fluidity changes in bacterial membranes. There is evidence that the coexistence of fluid and solid lipid domains facilitates transport through membranes.
Dynamic properties and membrane activity of ion specific antibiotics
Authors: Grell E. , Funck Th. 
Published: May 2005

AbstractConformational rearrangements of membrane‐active peptide and depsipeptide antibiotics such as enniatin B, valinomycin, and valine‐gramicidin A have been studied as a function of solvent polarity employing ultrasonic absorption methods. The results provide information about the number of occupied conformational states and their respective rates of interconversion. The interpretation of the results from kinetic measurements was confirmed by spectroscopic studies.The remarkable differences in the stabilities of the various cation complexes of depsipeptide antibiotics bound to lecithin vesicles as well as in homogeneous solution were related to different conformations of the ligands in these complexes as characterized by spectroscopic techniques. Kinetic studies by relaxation methods led to the elucidation of the mechanism of complex formation. Complexation of cations follows a multistep reaction. For valinomycin the rate‐limiting step of cation complexation is a ligand conformational change which occurs during the stepwise substitution of solvent molecules from the cation.
Bacterial mutants which block phage assembly
Authors: Georgopoulos Costa P. , Eisen Harvey 
Published: May 2005

AbstractgroE bacterial mutants of E. coli have been isolated on the basis of their inability to propagate bacteriophage λ. The block exerted on λ growth has been shown to operate at the level of head assembly. Some groE mutations express pleiotropic effects, such as inability to propagate T4 and T5 or inability to form colonies at high temperature. P1 transduction experiments show that these groE mutations map at 83 min on the genetic map of E. coli and that a single mutation is responsible for the pleiotropic effects observed. At 43°C, some of the groE strains are temperature sensitive for growth and form long filamentous structures. Examination of the proteins synthesized at 43° by one of the temperature‐sensitive groE strains, groEA44, by SDS gel electrophoresis reveals a pattern of synthesis somewhat different from that exhibited by the gro+ parent strain: some new bands appear, while others disappear.
Assembly of microtubules from preformed, ring‐shaped protofilaments and 6‐s tubulin
Authors: Erickson Harold P. 
Published: May 2005

AbstractTubulin obtained from disassembly of microtubules at 0°C exists in two forms: 6‐S tubulin and a larger, curved or ring‐shaped filament. These two forms have been separated chromat ographically and their roles in assembly examined. The purified rings reassemble to microtubules with high efficiency by uncoiling and straightening out, to be incorporated directly as protofilaments in the microtubule wall, and are thus identified as preformed protofilaments. Purified 6‐S tubulin has not been observed to reassemble into microtubules by itself but will contribute to assembly when mixed with rings. Addition of glycerol at 0°C induces the 6‐S tubulin to form rings, and the treated fraction will then reassemble to microtubules. Electron microscope observations indicate that assembly begins with the formation and growth of an incomplete microtubule wall. This wall grows wider by the addition of new protofilaments until the intact, circular microtubule, with 13 protofilaments, is formed. It is suggested here that growth of this wall from individual 6‐S tubulin subunits may be energetically unfavorable. The direct incorporation of preformed protofilaments may be much more favorable, in which case the rings would be required for this initial stage of assembly.
Regulation of size and birefringence of the in vivo mitotic apparatus
Authors: Rebhun Lionel I. , Mellon Margaret , Jemiolo David , Nath Jayasree , Ivy Nettie 
Published: May 2005

AbstractLong chain glycols augment in size and birefringence the in vivo mitotic apparatus (MA) of marine eggs. Dinitrophenol and caffeine antagonize the effect but they can be balanced by glycols. Caffeine inhibits the phosphodiesterase for cyclic AMP (CAMP) and CAMP levels increase in its presence. However, added dibutyryl CAMP does not affect MAs or cleavage, but is taken up by eggs. Oxygen uptake studies show that caffeine depresses oxidative metabolism but does not affect ATP levels. Action through the pentosephosphate shunt is suggested.Glycols influence the assembly of tubulin. Optical ultracentrifuge patterns of tubulin polymerized without glycol show a 6S and 30S peak. Similar patterns of tubulin polymerized at pH 6.4 in glycol and depolymerized in its absence show 6S, 8–18S, and 30S, peaks. The 8–18S peak appears in equilibrium with the 6S peak. If glycol is added to cold tubulin polymerized without glycol, only 6S and 30S peaks occur. Preparations with no 30S peak do not show 450 Å rings in the EM. Calcium depolymerizes microtubules. In the absence of glycols 450 Å rings are seen. In the presence of glycol, much higher concentrations of calcium are necessary for depolymerization, and few 450 Å rings occur.We suggest that glycols prevent formation of the stable 30S peak, favor an intermediate structure in equilibrium with the 6S peak, and antagonize calcium depolymerization. Their in vivo effects may arise from these interactions.
Lipid phase separations and protein distribution in membranes
Authors: Kleemann W. , Grant C. W. M. , McConnell H. M. 
Published: May 2005

AbstractLateral phase separations in lipid and lipid‐protein systems are discussed with the aid of phase diagrams derived from spin‐label measurements. Freeze‐fracture data from E. coli membranes and model lipid–protein bilayers indicate that the protein tends to associate with fluid lipid phases.
Interaction of enzymes with mixed micelles of phospholipid and detergent: Analysis of the phospholipase A2–dipalmitoyl phosphatidylcholine–triton X 100 system
Authors: Dennis Edward A. 
Published: May 2005

AbstractPhysical studies on the formation and structure of mixed micelles of the nonionic surfactant Triton X‐100 and phospholipids and enzymatic studies on the action of phospholipase A2 toward these mixed micelles are presented. Results of nmr intensity, line width, and T1 determinations, as well as gel chromatography and centrifugation experiments on the interaction of Triton X‐100 with egg and dipalmitoyl phosphatidylcholine, are presented and discussed. The structure of mixed micelles is discussed in terms of a working schematic model which is consistent with the experimental results. Kinetic studies on phospholipase A2 (Naja naja) action are then analyzed in terms of this model. The temperature dependence of phospholipase A2 action toward dipalmitoyl phosphatidylcholine is considered in terms of the effect of thermotropic phase transitions on mixed micelle formation. The phospholipase A2‐dipalmitoyl phosphatidylcholine‐Triton X‐100 system is then considered as an artificial model system for studying the effect of lipid phase separations on biological activity.
Nitrate reductase in E. coli: Properties of the enzyme and in vitro reconstitution from enzyme‐deficient mutants
Authors: MacGregor C. H. , Schnaitman C. A. 
Published: May 2005

AbstractThe nitrate reductase of E. coli is an inducible membrane protein with a molecular weight of about 800,000. The enzyme consists of four subunits of 60,000 molecular weight, four subunits of 142,000 molecular weight, four molecules of molybdenum, and nonheme iron. The enzyme may be solubilized by heat extraction, which results from limited digestion by a membrane‐bound protease, or by Triton X‐1 00. When the enzyme is isolated from Triton‐solubilized cytoplasmic membrane by immune precipitation, it contains a third protein of 20,000 molecular weight which may be a cytochrome.Chlorate resistant (chl) mutants of E. coli lack functional nitrate reductase. Mutants of the classes (chl)and chlB have all of the enzyme polypeptides present in the membrane JI intact form, while in classes chlC and chlE the membrane contains degraded fragments of the polypeptides, suggesting proteolysis of a defective enzyme. Reconstitution of nitrate reductase activity occurs when soluble extracts of various classes of mutants are mixed and incubated at 32°C. This reconstitution requires three things: (a) intact enzyme polypeptides in the form of small soluble lipoprotein fragments resulting from fragmentation of the cytoplasmic membrane during cell breakage; (b) a molybdenum factor which is present in the wild‐type membrane and which accumulates in the cytoplasm of chlB mutants in soluble form; and (c) a soluble factor or enzyme, presumably the chlB gene product, which adds the molybdenum factor to the enzymeTwo conclusions may be drawn from these observations. First, the enzyme is bound t o the membrane by small, hydrophobic regions on one or more of the subunits. Second, the process of reconstitution from mutant extracts is different from the process involved in de novo synthesis of the enzyme in wild‐type E. coli.
Structural changes in myosin during contraction and the state of ATP in the intact frog muscle
Authors: Bárány Michael , Bárány Kate , Burt C. Tyler , Glonek Thomas , Myers Terrell C. 
Published: May 2005

AbstractThe reactivity of myosin to [14C]‐labeled N‐ethylmaleimide ([14C] NEM) or to tritium was determined in functionally different frog muscles. The incorporation of [14C] NEM into myosin decreased during isotonic or isometric contractions, as compared to resting muscle. The cysteine residues which were protected during contraction were not involved in the ATPase activity or the actin‐binding ability of myosin. Peptide mapping revealed that several residues were protected simultaneously. The incorporation of tritium into the peptide N‐H groups of myosin was also decreased during muscle activity. These data support the idea that activation and subsequent contraction of muscle are correlated with structural changes in the myosin molecule.The reactivity of myosin to [14C] NEM was increased when the muscle was stretched to 140% rest length and treated with iodoacetate to deplete ATP. Based on in vitro experiments and on literature data, it is suggested that in the resting muscle myosin contains bound MgATP which decreases the rate of incorporation of [14C] NEM into myosin and that upon the irreversible loss of ATP the rate increases.31P nuclear magnetic resonance signals from a number of phosphates were detected in the intact frog muscle. The data indicated that the minimum concentration of ATP in the muscle is 3 mM, a value which agrees with that of chemical determination. The characteristic chemical shifts, coupling constants, and line widths of ATP in the muscle were considerably altered from that of either free ATP in aqueous solutions or ATP in perchloric acid extracts of muscle.
Isotopic probes of catalytic steps of myosin adenosine triphosphatase
Authors: Wolcott Robert G. , Boyer Paul D. 
Published: May 2005

AbstractA new approach to the direct estimation of the value of the off constant for dissociation of ATP from myosin subfragment 1 (S1) has been developed. From measurements of the extremely slow rate of release of [32P]‐ATP formed from 32Pi by S1 catalysis and the amount of rapidly formed [32P]‐ATP tightly bound to S1, the value of the off constant is approximately 2.8 × 10−4 sec−1 at pH 7.4.The concentration dependencies for Pi ⇌ H18 OH exchange and for 32Pi incorporation into myosin‐bound ATP give direct measurements of the dissociation constant of Pi from S1. Both approaches show that the enzyme has a very low affinity for Pi, with an apparent Kd of > 400 mM.Measurement of the average number of water oxygens incorporated into Pi released from ATP by S1‐catalyzed hydrolysis in the presence of Mg2+ suggests that the hydrolytic step reverses an average of at least 5.5 times for each ATP cleaved. With the Ca2+‐activated hydrolysis, less than one oxygen from water appears in each Pi released. This finding is indicative of a possible isotope effect in the attack of water on the terminal phosphoryl group of ATP.