bluuebunny/crossref_metadata_2025_split huggingface dataset:
Near‐infrared fourier transform Raman spectroscopy of indigoids
Authors: Tatsch Ellen , Schrader Bernhard 
Published: May 2005

AbstractNear‐infrared Fourier transform Raman spectra (3400 to — 20 cm−1) for the solid phases of indigo, thioindigo, selenoindigo and N,N'‐dimethylindigo were recorded with excitation using Nd:YAG laser radiation at 1064 nm. A complete vibrational assignment is proposed supported by the results of ab initio calculations. The spectra are complementary to the IR spectra recorded earlier. They also complete earlier results of resonance Raman spectroscopy. The spectra support a molecular structure of the indigo chromophore with a cross‐conjugated vinylogue amide system.
Raman and infrared spectra, conformational stability, barriers to internal rotation and ab initio calculations of trifluoroacetyl isothiocyanate
Authors: Durig J. R. , Guirgis Gamil A. , Krutules K. A. 
Published: May 2005

AbstractThe Raman (3100‐10 cm−1) and infrared (3100‐30 cm−1) spectra of trifluoroacetyl isothiocyanate [CF3C(O)NCS] were recorded for the gas and solid. Additionally, the Raman spectrum of the liquid was recorded and qualitative depolarization values were obtained. The observed bands are assigned on the basis of the more stable cis conformer (isothiocyanate group cis to the carbonyl bond) and the less stable trans conformer in the vapor state. From the variable‐temperature studies of the infrared spectrum of the sample dissolved in liquified xenon, two conformer pairs were used to determine a ΔH value of 104 ± 9 cm−1 (270 ± 26 cal mol−1). From the temperature dependence of the Raman spectrum of the liquid, two conformer pairs were used to determine experimentally a ΔH value of 90 ± 31 cm−1 (258 ± 88 cal mol−1), but for this physical state the trans conformer is the more stable form. In the annealed crystalline solid, only the trans conformer remains. A complete vibrational assignment is proposed for both conformers based on infrared band contours, Raman depolarization data, group wavenumbers and normal coordinate calculations. The experimental conformational stability, barriers to internal rotation and fundamental vibrational wavenumbers are compared with those obtained from the ab initio calculations employing the RHF/6‐31G* basis set and to the corresponding quantities obtained for some similar molecules.
Femtosecond time‐resolved vibrational spectroscopy of heme proteins
Authors: Zhu Leyun , Wang Wei , Sage J. Timothy , Champion Paul M. 
Published: May 2005

AbstractUltra‐fast pulsed laser measurements in the time domain have several advantages over traditional frequency‐domain spectroscopy. For example, very low frequency modes are more easily probed, fluorescent samples can be studied and vibrational modes that are directly coupled to chemical reactions are revealed. This study demonstrated some of these advantages using heme protein samples. Low‐frequency modes are observed in deoxymyoglobin (deoxyMb), fluorescence rejection is demonstrated with metMb and product‐state vibrational coherence is revealed with MbNO.
Anisotropy as an ultrafast probe of electronic coherence in degenerate systems exhibiting Raman scattering, fluorescence, transient absorption and chemical reactions
Authors: Wynne Klaas , Hochstrasser R. M. 
Published: May 2005

AbstractThe effects of electronic coherence of doubly or triply degenerate levels are discussed. This coherence will show up in the anisotropy of a pump—probe experiment in which a pump pulse creates the coherence and a probe pulse connects the degenerate levels to a non‐degenerate final state. Simple stochastic models for the decay of the anisotropy as a function of pump—probe delay are given, both for molecules with a high symmetry and for symmetric dimers and trimers. The possible role that degenerate level coherence may play in chemical reactions is also discussed. Finally, the stochastic models used to calculate the anisotropy decay are applied towards the calculation of absorption line shapes, Raman scattering and fluorescence.
Fourier transform Raman spectroscopic study of hydrogen bonding in 2,5‐dimercapto‐1,3,4‐thiadiazole using an environmental chamber
Authors: Lawson E. E. , Edwards H. G. M. , Johnson A. F. 
Published: May 2005

AbstractThe bands at 2485 and 940 cm−1 observed in the Raman spectra of 2,5‐dimercapto‐1,3,4‐thiadiazole represent the hydrogen‐bonded ν(SH) stretching and δ(C‐SH) in‐plane bending modes, respectively. A quantitative study of the hydrogen bonding was carried out using intensity measurements of the bands assigned to the hydrogen‐bonded and the free δ(C‐SH) in‐plane deformations at 940 and 919 cm−1, respectively, as a function of temperature. The Fourier transform (FT) Raman spectra were recorded over the temperature range 303‐403 K using an environmental chamber fitted into the FT Raman sample compartment. The equilibrium constants between the free and the hydrogen‐bonded molecules were determined over this temperature range and the average enthalpy for hydrogen‐bond formation was obtained (ΔH° = −3.35 ± 0.2 kJ mol−1).
Vibrational characterization of Langmuir—Blodgett films of octa‐(15‐crown‐5)‐lutetium bisphthalocyanine
Authors: Rodríguez‐Méndez M. L. , Souto J. , De Saja J. A. 
Published: May 2005

AbstractSurface‐enhanced resonant Raman scattering and Fourier transform surface‐enhanced Raman scattering of Langmuir‐Blodgett monolayers of the green and blue forms of octa‐(15‐crown‐5)‐lutetium bisphtalocyanine prepared on gold island films are reported. The spectroscopic characterization was completed by measuring the Raman and Fourier transform infrared spectra of dispersions of the materials in KBr matrices. An empirical vibrational assignment of the observed fundamentals is given.
Fourier transform Raman spectroscopic study of lithium perchlorate solutions in acrylonitrile
Authors: Alia J. M. , Edwards H. G. M. , Moore J. 
Published: May 2005

AbstractLithium perchlorate solutions in acrylonitrile (propenenitrile), in a range of concentration between 1 and 6 molal, were studied by using Fourier transform Raman spectroscopy. The new band in the v(CN) region proceeding from the bound species Li+… (acrylonitrile)n and the modifications in the C—C stretching band were studied in detail by means of deconvolution and band‐fitting procedures. An average solvation number of ca. 2.3 was obtained without any correction for the ion pairing. The data obtained in the analysis of the perchlorate anion v1 (symmetric stretch) band allow us to quantify the concentration of the different species (free perchlorate, solvent‐separated ion pairs and contact ion pairs) present, and to obtain a more realistic solvation number for the lithium ion in acrylonitrile solutions. This solvation number was estimated at 3.0 ± 0.1.
Remote Raman spectroscopic studies of corrosion products formed on nuclear fuel claddings used in PWR and AGR systems
Authors: Edwards H. G. M. , Long D. A. , Willis I. T. 
Published: May 2005

AbstractThe construction of a remote Raman microscope system with a variable microscope‐to‐spectrometer distance of up to 3 m is described. Oxidative surface corrosion products on zirconium alloy and stainless‐steel nuclear fuel claddings for pressurized water and advanced gas cooled reactor systems produced under various conditions were studied and the potential of the technique for in situ analysis is discussed. Under the conditions studied experimentally, the major corrosion products are found to be α‐ZrO2 and α‐Fe2O3 for the zirconium alloy and stainless‐steel claddings, respectively.
Surface enhanced resonance Raman scattering from cyanocobalamin and 5′‐deoxyadenosylcobalamin
Authors: Quaroni L. , Reglinski J. , Smith W. E. 
Published: May 2005

AbstractSurface enhanced resonance Raman scattering (SERRS) from cobalamins is reported. To achieve efficient adsorption and strong SERRS, the molecule is adsorbed on a polysine‐treated silver colloid surface. This provides an organic barrier between the cobalamin and the metal, preventing denaturation, and gives positively charged groups for efficient adsorption. The technique can be used for in situ studies of changes in the metal coordination sphere, as is illustrated by reduction on the surface using dithionite for both cyanocobalamin and 5′‐deoxyadenosylcobalamin. The efficient energy transfer at the surface appears to prevent photodegradation, which is a problem with resonance, and the efficiency of SERRS allows measurements at low effective concentrations.
Cell surface glycoproteins I: Accumulation of a glycoprotein on the outer surface of mouse LS cells during mitosis
Authors: Brown J. C. 
Published: May 2005

AbstractSurface glycopeptides derived from vertebrate cells have been separated into 4 classes by chromatography on DEAE cellulose columns. Among different cell types tested, significant differences were observed in the relative amounts of these 4 glycopeptide classes present on the cell surface. This type of heterogeneity is consistent with the expected biological role of cell surface glycoproteins. One glycopeptide, as revealed by the DEAE column analysis, was found to have a characteristic metabolic pattern in mouse LS cells. New accumulation of this structure, called glycopeptide 4, on the cell surface was detected only around the period of cell division (M phase) and not at other times during the cell cycle.
Regulation of polar cap formation in the life cycle of Escherichia coli
Authors: Hoffmann Björn , Messer Walter , Schwarz Uli 
Published: May 2005

AbstractPolar cap formation has been studied in synchronized Escherichia coli cells. It is dependent on a signal given after completion of a round of DNA replication. A 20 min time interval between the release of this signal and physical cell separation is probably the time required for the completion of polar caps. During this time murein is synthesized at an increased rate and cells are especially sensitive to penicillin.
Composition, structure and phase transition in yeast fatty acid auxotroph membranes: Spin labels and freeze‐fracture
Authors: James Robert , Branton Daniel , Wisnieski Bernadine , Keith Alec 
Published: May 2005

Abstract
Fatty acid desaturase mutant yeast cells have been enriched with 2 fatty acids having substantially different physical properties.
Differences in fatty acid composition are reflected in the ESR determined phase transitions and the freeze‐fracture morphology of the tonoplast.
In these cells, fatty acid composition, rather than the position of the phase transition relative to growth temperature, appears to be the more important variable in determining membrane morphology.
The freezing process used in the freeze‐fracture technique does not appear to cause a demixing of the lipid components of the membrane.
Study of envelope proteins in E. coli cet and recA mutants by SDS acrylamide gel electrophoresis
Authors: Holland I. B. , Tuckett Susan 
Published: May 2005

AbstractDisc‐electrophoresis of E. coli envelope proteins on SDS acrylamide gels reproducibly revealed up to 50 distinct polypeptide bands. Corresponding molecular weights ranged from 105,000 to 20,000 daltons or less. Major bands corresponded to molecular weights of 73,000, 48,000, 36,000 and 30,000 with the latter constituting up to 20% of the total envelope protein depending upon the method of isolation. Minimum levels of detection using stained gels equaled 0.25 μg protein or 1% of total sample analyzed; for a polypeptide of molecular weight 40,000 daltons this was calculated to be equivalent to 1,200 molecules per cell envelope. In envelopes from a cetB− mutant strain (refractory to colicin E2), an additional band, constituting up to 5% of the total envelope protein was present. The molecular weight of this protein, which was maximally present in wild type envelopes in only trace amounts, is 44,000 daltons, indicating a cellular concentration of approximately 6 × 103 molecules per envelope. This new band was not affected by heating envelope preparations to 100° prior to electrophoresis, but was largely eliminated by washing isolated envelopes in low ionic strength buffer, or by pre‐incubating cells with trypsin prior to preparation of envelopes. Treatment of isolated envelopes with Triton X‐100, which preferentially releases inner membrane proteins from the envelope (18), resulted in the extraction of a preponderance of the high molecular weight polypeptides, including the 44,000 dalton protein from envelopes of the mutant. The major polypeptides of the envelope and the low molecular weight components were not extracted by Triton X‐100. The properties of the 44,000 dalton protein indicated that it is relatively loosely associated with the surface envelope and may be exposed on the external surface of the cytoplasmic membrane. Possible explanations for the appearance of this protein in mutant strains and its relationship to the inability of these to respond, specifically to surface bound colicin E2, will be discussed. Extensive analysis of envelopes from recA− mutants was also carried out and revealed an unusual amount of variation in polypeptide profiles obtained from different preparations. However, no consistent quantitative or qualitative difference between recA and rec+ strains was obtained. In recA, cetB double mutants, the increased level of the 44,000 dalton polypeptide was identical to that found in the rec+, cetB mutant.
Fluorescence and circular dichroism studies on human serum low density lipoprotein particles and lipid‐depleted derivatives
Authors: Pollard Harvey B. , Chen Raymond F. 
Published: May 2005

AbstractThe low density liporpotein from human serum, and derivitives prepared free of neutral lipids and total lipids, have been studied by fluorescence and circular dichorism methods. Removal of the neutral lipids had little effect on the tryptophan fluorescence at neutral pH. However, by the criteria of circular dichroism, over the range of 200 nm to 250 nm, there was a reduction in secondary structure of over 75%. Removal of the remaining phospholipids resulted in a qualitatively different structure by both fluorescence and circular dichroism criteria.Neutral lipids were removed from LDL in a step‐wise fashion in order to determine the exact amount of neutral lipid required for the native circular dichroism spectrum. The circular dichroism band intensity was constant until approximately 10% of the total cholesterol (as cholesterol ester) remained. The intensity then abruptly dropped as more cholesterol was removed.We concluded that the two spectroscopic methods report on two distinct aspects of LDL structure. The tryptophan fluorescence appears to be sensitive to the presence of phospholipids. The circular dichroism, however, appears to be sensitive to the binding of a small amount of neutral lipid. These findings suggest that a functional and geometric separation of binding sites may exist for these two classes of lipids. Such a distinction is predicted by the icosohedral model of the quaternary structure of LDL. In this model, the phospholipids are located on the surface of the particle, in the holes of an icosohedrally symmetric surface network of protein subunits; the neutral lipids are located in the particle core.Finally, we suggest that functional significance may be attached to our finding that relatively few cholesterol ester molecles are needed to maintain the native secondary structure of LDL. This provides a mechanism whereby the amount of bound neutral lipid could be raised or lowered (for transport and transfer to cells) without affecting the protein in any structurally significant manner.
Protein composition of cell and forespore membranes of Bacillus subtilis
Authors: Goldman Robert C. 
Published: May 2005

AbstractA sporulation mutant of Bacillus subtilis 168 was isolated and characterized. The mutant, designated SB‐23, releases viable forespores at the end of the developmental period. Forespores were isolated on linear Renografin gradients and used as a source of forespore membranes. The protein composition of forespore membranes was found to differ from the protein composition of vegetative cell membranes by discgel electrophoresis. The results are discussed in relationship to morphological and physiological differentiation during bacterial sporulation.
Isolation and characterization of a protease inhibitor from commercial stem bromelain acetone powder
Authors: Perlstein Seymour H. , Kéazdy Ferenc J. 
Published: May 2005

AbstractSeven closely related protease inhibitors were isolated from commercial bromelain acetone powder in electrophoretically pure form by gel filtration on Sephadex G‐75, followed by ion exchange chromatography on DEAE Sephadex at pH 7.55. The inhibitors are proteins of MW 5000‐6000, which inhibit competitively the bromelaincatalyzed hydrolysis of CLN (Ki ≈ 10−7 M). This inhibition is optimal at pH 3 to 4,. and it depends upon the ionization of two acidic residues of pK = 4.5 and 5.0. In the acidic pH range the inhibitors are also effective toward papain, ficin and trypsin.
Conformational aspects of rhodopsin and retinal disc membranes
Authors: Steinemann Adrian , Wu Cheng‐Wen , Stryer Lubert 
Published: May 2005

AbstractWe have used two experimental approaches – fluorescence spectroscopy and lectin binding – to obtain information about the structure of rhodopsin and its position in retinal disc membranes. Energy transfer was used as a spectroscopic ruler to deduce proximity relationships in rhodopsin and in disc membranes. Concanavalin A and wheat germ agglutinin served as specific macromolecular probes of the accessibility of the carbohydrate unit of rhodopsin in disc membranes. We infer from these studies that: (1) The rhodopsin molecule is at least 75 Å long and has an elongated shape. (2) There may be distinct hydrophobic and hydrophobic and hydrophilic domains in rhodopsin. (3) The carbohydrate moiety of rhodopsin is on the surface of the disc membrane, probably only on the external face. (4) The disc membrane has an asymmetric structure. (5) The external surface of the disc membrane is closer to site A (a sulfhydryl residue on rhodopsin) than to 11–cis retinal.
Rhodopsin–lipid interactions
Authors: Hong Keelung , Chen Yong Shiau , Hubbell Wayne L. 
Published: May 2005

AbstractPurified, lipid‐free rhodopsin has been incorporated into bilayers of natural and synthetic phosphatidyl cholines and a natural digalactosyl diglyceride. Successful incorporation and high regenerability of rhodopsin appears to depend on the nature of the hydrocarbon chains and not specifically on the type of polar head group of the lipids.Electron paramagnetic resonance spectra of recombinant membranes containing small amounts of spin labeled phosphatidyl cholines reveals that rhodopsin interacts directly with the hydrocarbon chains of the phospholipids in the bilayer, resulting in a dramatically decreased motional freedom of the chains.In studies of the recombinant membranes using freeze–fracture electron microscopy, the presence of rhodopsin is detected as discrete particles in the plane of fracture. The particle distribution is dependent on the nature of the lipid hydrocarbon chains and whether or not the rhodopsin has been photolyzed.From these studies, it is concluded that the rhodopsin‐bilayer structure is stabilized primarily by direct interaction of the hydrocarbon chains with the protein molecule, and that structural parameters in this model system are subject to modulation by visible light.
Adenylate cyclase and cyclic AMP phosphodiesterase of normal and rous sarcoma virus transformed chicken embryo fibroblasts
Authors: Russell Tom R. , Anderson Wayne B. 
Published: May 2005

AbstractCyclic AMP appears to regulate cell growth. Cyclic AMP levels are high in normal chicken embryo fibroblasts and drop to very low levels when the cells are transformed by the Bryan high‐titer strain of Rous sarcoma virus. Cells infected with a temperature‐sensitive mutant of the virus have normal levels of cyclic AMP at the nonpermissive (nontransforming temperature), but when the cells are shifted to the permissive (transforming) temperature the cyclic AMP levels rapidly fall to values that are found in transformed cells. Studies on the adenylate cyclase and cyclic AMP phosphodiesterase in normal and transformed chicken embryo fibroblasts have shown that the adenylate cyclase is greatly decreased in the transformed cells whereas the phosphodiesterase is increased. The decrease in adenylate cylcase activity is the result of an increase in the Km of the substrate and a loss of a magnesium ion activator site. The increase in phosphodiesterase activity is the result of an increase in total phosphodiesterase activity and a decrease in the negative cooperativity of plasma membrane bound phosphodiesterase. Thus the fall in cyclic AMP levels that occurs on transformation can be correlated with changes in the activity of adenylate cyclase and cyclic AMP phosphodiesterase.
Red cell aggregation by macromolecules: Roles of surface adsorption and electrostatic repulsion
Authors: Chien Shu , Jan Kung‐Ming 
Published: May 2005

AbstractAggregation of normal and neuraminidase‐treated human red blood cells (RBC) by dextrans of various molecular sizes and concentrations was quantified by microscopic counting and light reflectometry. The influences of variations in the ionic strength and the cationic valency of the dextran solution on RBC aggregation were also investigated. The data on RBC aggregation were correlated with measurements of the zeta potential by cell electrophoresis and the intercellular distance in the rouleaux by electron microscopy. With the use of the classical equations and newly developed knowledge in colloid chemistry, the electrostatic repulsive force between adjacent cell surfaces (Fe) was calculated from the experimental data. The macromolecular bridging force causing RBC aggregation (Fb) has also been derived as a function of dextran concentration. Other forces that cause RBC disaggregation are the mechanical shearing force (Fs) and the RBC membrane bending force (Fm). The net force for RBC aggregation is equal to Fb – Fe – Fm – Fs. This model of aggregation involving force balance at the surface can explain known experimental results on factors influencing cell aggregation. It is proposed that such force balance between cell surfaces may be applicable in other cell or particulate systems and that it may be of fundamental importance in many physiological functions.
The surface chemistry of the erythrocyte and thrombocyte membrane
Authors: Seaman G. V. F. 
Published: May 2005

AbstractThe electrokinetic procedures used for investigation of the nature and distribution of cellular surface charge groups are outlined. The application of ion binding studies, the action of enzymes, and the effects of specific functional group reagents are illustrated by discussion of the results obtained for erythrocytes and thrombocytes. The human erythrocyte has been shown to be a macropolyanion possessing about 107 charged groups per cell of which more than 60% are the carboxyl group of N‐acetylneuraminic acids; some of the remaining groups at least are the α‐carboxyl groups of protein‐bound amino acids. The electrokinetic constitution of the human blood platelet is more complex and includes sialic acid carboxyl groups and phosphate groups and at least one other species of unidentified anionogenic groups as well as amino groups. Lastly the effects of neutral and charged polymer adsorption on the electrokinetic properties of blood cells are briefly considered.