bluuebunny/crossref_metadata_2025 huggingface dataset:
Vibrational contribution to the internal rotation potential of toluene and nitromethane
Authors: Grošev Vlasta Mohaček , Schrötter Heinz W. , Jonuscheit Joachim
Published: May 2005

The vibrational contribution to the internal rotation potential of toluene and nitromethane is calculated for different force fields which were constructed using permutation‐inversion group and dependent on the internal rotation angle. The assignments of Raman spectra were made using experimental data obtained for the liquid and vapour (toluene) states and supported by vibrational analysis calculation. The vibrational contribution calculated with a ρ‐independent force field represents the kinetic energy contribution to the internal rotation potential of the molecule in question. For toluene (C6H5CH3) and nitromethane (CH3NO2) the kinetic energy contribution is zero, and for C6D5CHD2 and CHD2NO2 it has a cos (2ρ) dependence. This sort of calculation may serve as a check of any force field used for assigning molecular vibrations by comparing calculated internal rotation potentials in excited vibrational states with the parameters of the potential found from the fit of vapour band contours.
End‐chain conformations of n‐alkane molecules in urea inclusion compounds: A Raman scattering study
Authors: Baghdadi Abdelkrim El , Guillaume François
Published: May 2005

Urea inclusion compounds containing n‐alkane (CnH2n+2 with n = 8 and 19) guest molecules were investigated by means of Raman spectroscopy. Vibrational modes due to the urea confirm the structural identify of the inclusion compounds, and lattice modes of the urea host structure were assigned tentatively. Investigations of the vibrational properties of the CnH2n+2 guest molecules were focused on the longitudinal accordion mode (LAM‐1) and the methyl rocking r(CH3) vibrations. These modes were studied as a function of (i) the length (n) of the guest molecule, (ii) temperature and (iii) pressure. The vibrational bands characteristic of the end‐gauche gt‐ and tg‐defects were therefore identified. From these results, trends in the relative amounts of gauche gt‐ end‐groups for the various guest molecules were assessed in both the low‐ and high‐temperature structural phases of the compounds and found to be constant and of the order of ca. 5%. It was also shown that the amount of n‐alkane chains distorted at their ends depends markedly on the hydrostatic pressure. These results are discussed and compared with literature data.
Method for the determination of spectral shifts in Raman spectroscopy
Authors: Gaufrès Robert , Huguet Patrice , Arab Youssef
Published: May 2005

A new method for the determination of the wavenumber shift between two bands was developed. It rests on the mathematical properties of the absolute area of a difference spectrum, previously proved by the authors. Its field of application is wider than that of the method used up to now, as it allows the determination of the shift between two bands of any profile, provided that the profiles of these bands are identical, and between bands of different profiles, provided that they are symmetrical. No approximation, unless completely justified, is involved in this method. It is exemplified by some experiments which demonstrate its accuracy. A final experiment shows the possibility of determining a Raman shift between two liquid samples using a classical device, with fair accuracy.
Analysis of polarized Raman spectra of liquids at liquid—solid interfaces
Authors: Bousquet C. , Masson M. , Harrand M.
Published: May 2005

Polarized Raman spectra of liquids within a solid—liquid interface were analysed. The liquid, deposited on the solid surface, is illuminated by an evanescent electromagnetic wave; the penetration depth is l ≤ 100 nm. Interface liquid spectra are compared with the polarized spectra of the isotropic liquid. It is found that the changes observed in the spectra cannot be explained merely by structural changes in the molecules; the influence of changes in the main characteristics of the exciting electric field, arising from defects of the solid surface, must also be considered. With rutile surfaces, the experimental spectra are linear combinations of the isotropic liquid spectra; the electric field, partially depolarized by the surface defects, is still a long‐range field: no structural changes for the molecules are found within the illuminated part of the interface. With thin silver film‐coated surfaces, however, the spectra cannot be reduced to linear combinations of the liquid spectra. Structural changes for the molecules are also involved. The electric field is enhanced by the excitation of the surface plasmon of silver but, because of the surface defects, the field, partially depolarized, spreads over a range much shorter than l, and is strongly dependent on the defect geometry. The short‐range enhancement can mask a possible further orientation of the molecules, preventing any determination of the range of the solid—liquid interaction. Time dependence of the spectra related to an increase in the silver surface roughness leads to surface‐enhanced Raman scattering (SERS).
Raman spectroscopic studies of α‐NaVO3, β‐NaVO3 and NaVO3 · 2H2O
Authors: Kuok M. H. , Tang S. H. , Shen Z. X. , Ong C. W.
Published: May 2005

Sodium metavanadates in α (α‐NaVO3), β (β‐NaVO3) and hydrated (NaVO3 · 2H2O) forms were studied down to 10 K. All the phases were found to be stable at low temperatures. The hydrated to β transformation above room temperature was found to occur at 305 K. This transition is first order and most likely a one‐step process, rather than a two‐step process as had been suggested previously.
Accurate relative calibration of a multi‐channel Raman spectrometer
Authors: Huguet Patrice , Gaufrès Robert
Published: May 2005

A method of restoring a given spectral position of a multi‐channel Raman spectrometer is described. With a spectrometer, the wavenumber counter of which is graduated in cm−1 and the dispersion on the detector is about 0.7—0.9 cm−1 per photodiode, the standard deviation about a mean position is shown to be 0.15 cm−1 when this method is used.
Determination of the temperature of a gas by a simple and accurate Raman method
Authors: Huguet Patrice , Gaufrès Robert
Published: May 2005

A method for the determination of the temperature of a gas by means of the absolute area of a Raman difference spectrum is described. Its versatility and accuracy are briefly discussed.
Depolarized rayleigh wing from Raman spectra and local order in pure C6H6 and C6F6 liquids and in their binary mixtures
Authors: Dayan E. , Loisel J. , Berreby L. , Dervil E. , Pinan‐Lucarré J. P.
Published: May 2005

From Raman spectra, the low‐wavenumber range profile (10‐200 cm−1) of planar molecules C6H6, C6F6 and of their binary mixtures in the liquid state was recorded at intervals of 1°C from 10 to 65°C. The analysis was made using a reduced intensity ratio R involving the integrated intensity of a constructed I(v)v2 spectrum and the recorded I(v) spectrum. The study of R against a slow and gradual variation of temperature emphasized a break in the gradient for pure liquids. This effect is related to a change in the local environment of the molecules. This break did not appear in the study of a 1:1 mixture owing to its strong stability due to a face‐to‐face configuration.
SERS and SERS of Langmuir—Blodgett monolayers: Surface coverage dependence at room and low temperature
Authors: Menéndez J. R. , Martin Fernando
Published: May 2005

SERRS intensity patterns versus surface molecular coverage, both at room temperature and at low temperature (liquid N2), were studied using mixed Langmuit‐Blodgett (LB) monolayers of tetra‐tert‐butylvanadyl‐phthalocyanine and lutetium bisphthalocyanine with arachidic acid. The role played by temperature variations in the surface coverage dependence and SERRS intensity patterns is analysed.
Raman spectroscopy of bismuth tungstates
Authors: Hardcastle Franklin D. , Wachs Israel E.
Published: May 2005

The Bi2O3‐WO3 system was examined using Raman spectroscopy. The Raman spectra of bismuth tungstate samples having Bi: W ratios of 2:1, 4:1 and 14:1 were used to identify the bismuth tungstate phases present at these compositions. The bismuth tungstate phases which occur were found to depend on the Bi: W ratio. The 2:1 composition consists of only the Bi2WO6 phase and the 14:1 composition consists almost entirely of the sillenite phase. The 4:1 composition, however, is multi‐phase and consists of Bi2WO6, the sillenite phase, and another phase referred to as 7Bi2O3‐2WO3. The Raman spectra were used to determine the coordination of the tungstate species as well as their WO bond lengths in each of these phases.
Study of β‐carotene by time and wavenumber domain coherent anti‐stokes Raman scattering techniques
Authors: Kummrow Andreas , Lau Albrecht
Published: May 2005

Dephasing of vibrations of all‐trans‐β‐carotene in cyclohexane was studied by resonance CARS in the wavenumber domain, using scanning CARS, and also in the time domain, by interferometric CARS (I‐CARS) applying temporally incoherent light from non‐transform limited broadband lasers. The ground‐state vibrations (1002, 1153, 1188, 1210 and 1522 cm−1) are predominantly homogeneously broadened and have dephasing times ranging from 0.6 to 0.7 ps. For broadband wavenumbers in the long‐wavelength wing of the absorption band and a Stokes laser intensity exceeding 0.5 GW cm−2, the CARS signal saturates and decreases above 1 GW cm−2. The decrease in the CARS signal is accompanied by the appearance of additional Raman lines. Taking into account all these Raman lines (solvent lines and two additional very broad lines), the features of the I‐CARS can be explained with the same parameters as for scanning CARS. Consideration of these additional lines is essential. Using excitation wavenumbers within the absorption band, power broadening of the 1522 cm−1 line is observed. In some experiments, diffraction by a laser‐induced grating strongly competes with I‐CARS.
Fourier transform surface‐enhanced Raman scattering for the detection and identification of polyaromatic hydrocarbons
Authors: Stewart S. D. , Fredericks P. M.
Published: May 2005

Fourier transform surface‐enhanced Raman (FT‐SER) spectra of 18 polyaromatic hydrocarbons (PAHs) were measured on a silver surface which had been previously roughened by an oxidation‐reduction procedure in an electrochemical cell. The sample was placed on the clean surface as a solution in an organic solvent and the solvent allowed to evaporate. All the samples had significantly different SER spectra. Detection limits were around 10−9 mol for most compounds but were higher for a few compounds, particularly azulene. For most samples the SER spectrum obtained was similar to the FT‐Raman spectrum of the solid sample. For one sample, azulene, a different spectrum was obtained by the SER technique, indicating a different, or additional, SER mechanism for this sample. A brief investigation of the quantitative aspects of the technique showed that, over the range studied, the intensity of the SER spectrum was related linearly to the amount of compound present on the surface.
Interactions in liquid mixtures of formamide isotopomers studied by Raman spectroscopy
Authors: Mortensen A. , Nielsen O. Faurskov , Yarwood J. , Shelley V.
Published: May 2005

Recently, anomalies concerning both intensities and peak positions of Raman bands in the carbonyl stretching region of liquid mixtures of different isotopomers of formamide were reported. More detailed investigations have now been performed for liquid mixtures of HCONH2 and H13CONH2, and Raman spectra of mixtures of DCONH2 and DCOND2 in the carbonyl stretching region are presented. In the system DCONH2‐DCOND2, collapse of the isotropic carbonyl bands was observed in the mixtures as previously reported for HCONH2‐HCOND2 and HCOND2‐DCOND2. The system HCONH2—H13CONH2 shows anomalous intensities compared with those expected for simple binary mixtures. However, this system does not show collapsing carbonyl bands in the isotopomeric mixtures. The phenomenon of collapsing bands can be explained in terms of a model known as mutual entrainment.
Non‐destructive ‘in situ’ Raman study of artistic glasses
Authors: Bertoluzza A. , Cacciari S. , Cristini G. , Fagnano C. , Tinit A.
Published: May 2005

A non‐destructive ‘in situ’ Raman spectroscopic study was carried out on 28 artistic glasses grouped in eight age classes between 1750 and 1940, in order to characterize the authenticity (age) of these objects. Other non‐‘in situ’ instrumental methods which require only micro amounts of sample, should be avoided in this case owing to the great brittleness of the samples. Although it was not found possible to characterize the age of the samples from the Raman spectra, which were very similar for all the different glasses examined, nevertheless, the intensity of the fluorescence band increased with the age of the samples. The logarithm of the ratio between the 1080 cm−1 Raman band intensity and that of the fluorescence band, obtained from the spectra where the fluorescence band was kept at the same intensity for the different samples, shows a linear relationship with the age of the glasses, and therefore constitutes a spectroscopic marker for the characterization of the authenticity of the samples.
Raman and infrared spectra, conformational stability, vibrational assignment and ab initio calculations for ethyl chloroformate
Authors: Bohets H. , van der Veken B. J.
Published: May 2005

Infrared (4000‐50 cm−1) spectra of gaseous, amorphous and crystalline solid ethyl chloroformate, ClCOOCH2CH3, and mid‐infrared spectra (4000‐500 cm−1) of the chloroformate dissolved in liquefied krypton were recorded. Raman spectra of the liquid and solid phases were investigated from 4000 to 50 cm−1. MP2 and RHF ab initio calculations were carried out using a 6—31G* basis set. The calculations show that the compound can occur as the s‐cis,trans, the s‐cis,gauche, the s‐trans,trans and the s‐trans,gauche conformers. For each conformer the optimized structural parameters, the vibrational wavenumbers, infrared intensities, Raman scattering activities and potential energy distributions were calculated. Both s‐cis conformers were identified in the vibrational spectra of all non‐crystalline phases. Evidence for the presence of the s‐trans conformers is found in the liquid‐phase Raman spectra. The enthalpy difference between the s‐cis,gauche and s‐cis,trans conformers was determined in the pure liquid phase to be 3.2 ± 0.3 kJ mol−1. Also in the liquid phase, the enthalpy difference between the observed s‐trans and the s‐cis,trans conformers was determined to be 14.3 ± 0.8 kJ mol−1. Vibrational spectra of the crystalline solid, which contains only the s‐cis,trans conformer, showed that ethyl chloroformate can crystallize in two different forms. A complete assignment of the infrared and Raman spectra is proposed.
Infrared and Raman spectra of L‐asparagine and L‐asparagine‐d5 in the solid state
Authors: Casado J. , LÓPez Navarrete J. T. , Ramírez F. J.
Published: May 2005

The infrared and Raman spectra of L‐asparagine and ND3+, ND2‐L‐asparagine as solid samples were recorded. The data obtained were used to propose a general assignment of the fundamental vibrational modes on the basis of the measured isotopic shifts and correlations with previous data reported for other amino acids and related molecules.
Influence of Pt—Cl force constants on the Raman lineshapes in Pt35Cl/37Cl chains
Authors: Bardeau J. F. , Bulou A. , Swanson B. I.
Published: May 2005

The influence of the 35 Cl/37 Cl isotopic disorder of natural chlorine on the Raman and infrared lineshapes of the vibrational modes in PtCl chains was calculated as a function of the interionic force constants in a one‐dimensional model. It is shown that the fine structure of the Raman line is strongly dependent of the Pt3+σ‐Cl and Pt3‐σ‐Cl force constants, and so it can be used to estimate the charge disproportion σ. From the case of [Pt(en)2][Pt(en)2Cl2](ClO4)4 it appears that the description of the high‐wavenumber infrared line (v2) requires one to take into account interactions with more distantations. It is also shown that the intensity of the lowwavenumber infrared‐active mode (v3) is so weak that the corresponding line may have never been observed.
Polysaccharide vibrational Raman optical activity: Laminarin and pullulan
Authors: Bell Alasdair F. , Hecht Lutz , Barren Laurence D.
Published: May 2005

The backscattered Raman optical activity (ROA) spectra of the β(1‐3)‐linked polysaccharide laminarin, and its dimer repeating unit D‐laminarihiose, together with those of the predominantly α(l‐4)‐linked polysaccharide pullulan, and its trimer repeating unit D‐maltotriose, between 350 and 1500 cm−1 in aqueous solution are reported and discussed. Several differences are evident between the ROA spectra of laminarin and D‐laminaribiose which are ascribed to triple helix formation in the polysaccharide. In particular, the signs of four ROA signals between ca. 1050 and 1150 cm−1 are reversed and two ROA signals assigned to vibrations involving the glycosidic link observed at ca. 445 and 1431 cm−1 change sign and increase in intensity, respectively. In contrast, pullulan, which adopts a random coil‐type structure in aqueous solution, generates an ROA spectrum that closely resembles that of D‐maltotriose.
Structure of the lipid phase of rauscher murine leukemia virus
Authors: Landsberger Frank R. , Lenard John , Compans Richard W. , Paxton John
Published: May 2005

The lipid‐containing membrane of Rauscher murine leukemia virus was studied using stearic acid spin labels with the nitroxide ring on the C5 and C16 positions. The environment of the C5 spin label was found to be much more rigid than that of the C16 spin label. This result, which parallels similar observations in red cell membranes and influenza virus, suggests that the lipid phase of Rauscher murine leukemia virus is arranged in a bilayer.
Four gel systems for electrophoretic fractionation of membrane proteins using ionic detergents
Authors: Fairbanks Grant , Avruch Joseph
Published: May 2005

Membrane proteins were fractionated electrophoretically in polyacrylamide gels containing either anionic or cationic detergent at either pH 2.4 or 8.3. In all four systems, polypeptides migrated as monomers bearing the charge of the detergent ion and semi‐logarithmic molecular weight–mobility relationships pertained. Electrophoresis of erythrocyte membrane proteins in these systems yielded very similar protein staining patterns but revealed significant differences in sialoglycoprotein migration.
Cis‐ and trans‐ membrane control of cell surface topography
Authors: Nicolson Garth L.
Published: May 2005

The topographic distributions of cell surface components can be modified by perturbations from the cell membrane exterior (cis‐membrane effect) or by perturbations from the cell interior that are transferred across the membrane (trans‐membrane effect). Using the human erythrocyte ghost as a model system, cis‐membrane effects on the topography of anionic sites were produced in B+ ghosts with anti‐B sera (but not with anti‐A), R. communis agglutinin and concanavalin A (but not with D. biflorus agglutinin). Cis‐membrane linkage was monitored by the state of aggregation of membrane‐bound colloidal iron hydroxide particles which bind almost exclusively to neuraminidase‐sensitive N‐acetylneuraminic acid residues on the outer surface. Trans‐membrane effects were observed when purified antibodies against an inner surface membrane protein, spectrin, were sequestered inside the ghosts. The sequestered antispectrin bound to spectrin at inner membrane surface and caused aggregation of the anionic sites on the outer membrane surface. The trans‐membrane effects of antispectrin required intact γG antibodies (Fab would not substitute) and was time‐ and concentration‐dependent.
Correlations between fatty acid distribution in phospholipids and the temperature dependence of membrane physical state
Authors: Linden C. D. , Keith A. D. , Fox C. F.
Published: May 2005

Cytoplasmic membranes of an unsaturated fatty acid auxotroph of Escherichia coli have been studied using spin labeled hydrocarbon probes. These studies reveal that the membrane lipids undergo changes of state at critical temperatures which reflect the physical properties of the fatty acid supplement supplied to the cells during growth. The critical temperatures observed in spin labeled membranes correlate with characteristic temperatures in membrane functions. Lipid analysis reveals that fatty acid composition and distribution in membrane phospholipids are primary determinants of the temperatures at which changes of state are observed in membrane lipids. Fatty acid composition and distribution can also produce unique interactions between certain spin label probes and their lipid environment.
A comparison of characteristic temperatures for transport in two unsaturated fatty acid auxotrophs of escherichia coli
Authors: Linden Carol D. , Fox C. Fred
Published: May 2005

The rate of sugar transport as a function of temperature has been compared in two unsaturated fatty acid auxotrophs. One of these, the parent strain 30E, can β‐oxidize the unsaturated fatty acid supplements, whereas the β‐oxidation defective progeny strain 30Eβox− cannot. In a previous study, Arrhenius plots for transport of β‐glucosides and β‐galactosides by strain 30Eβox− revealed striking departures from linearity at both a lower and an upper characteristic temperatures. By electron spin resonance (esr) these temperatures were shown to correlate with the temperatures where the membrane lipids undergo a transition from a totally solid state to a solid–liquid equilibrium and from a solid–liquid equilibrium to a totally liquid state, respectively (1). In the present study with strain 30E we have made the following observations:

Arrhenius plots for transport rate are usually more complex, often revealing three characteristic temperatures. Two of these correlate with the upper and lower characteristic temperatures observed in strain 30Eβox−. The third characteristic temperature falls between the previously described upper and lower ones.

In cells supplemented during growth with elaidate, the third characteristic temperature was identical within experimental limits for both β‐glucoside and β‐galactoside transport. indicating that it is likely to arise from some interaction in the bulk lipid phase. This conclusion is supported by the fact that the boundary of a change in physical state is also observed at this temperature by electron spin resonance.

In cells supplemented during growth with oleate, two or three characteristic temperatures were observed depending upon the transport system studied. Although glucoside and galactoside transport had the same lower characteristic temperature, these systems had no common upper characteristic temperature.

In cells supplemented during growth with the lipid density label, bromostearic acid, three characteristic temperatures were observed for β‐glucoside transport in both strains 30E and 30Eβox−.
Membrane assembly in escherichia coli V. Subcellular localization of phospholipid biosynthesis
Authors: Machtiger Neal A. , Fox C. Fred
Published: May 2005

The subcellular distribution of enzymes involved in lipid biosynthesis in E. coli K12 has been studied following various modes of cell disruption and fractionation of the subcellular components. Though most biosynthetic enzymes were found associated with the cytoplasmic membrane fraction regardless of the procédures of disruption or fractionation employed, the enzymes responsible for the synthesis of the major lipid of E. coli (phosphatidylethanolamine) and of its precursor (phosphatidylserine) had no distinct localization in extracts. These findings are discussed in the context of current models for the assembly of bacterial membranes.
Self‐assembly of collagen
Authors: Fessler John H.
Published: May 2005

The structure and self‐assembly of collagen and procollagen molecules are reviewed. The registration peptides of procollagen have specific recognition properties which assure (1) selection of component polypeptide chains and (2) registration of their N‐termini, facilitating orderly folding into a collagen helix. The stability of this helix relative to body temperature is critically altered by post‐ribosomal hydroxylation of proline residues. The registration peptides of procollagen may have additional functions such as preventing intracellular fiber formation.
Renaturation of disulfide‐linked procollagen
Authors: Fessler Liselotte I. , Rudd Colette , Fessler John H.
Published: May 2005

Disulfide‐linked, triple‐stranded procollagen (pro γ 112) was isolated from chick embryo skull bones. It was reversibly denatured and renatured as judged by sedimentation properties and susceptibility to digestion with pepsin. Refolding was an intramolecular process and aggregation between molecules did not occur.
Some symmetry considerations for the fibrinogen‐fibrin assembly system
Authors: Doolittle Russell F.
Published: May 2005

The formation of fibrin gels involves many operations which are fundamental to other assembly schemes, including limited proteolysis, spontaneous associations, and covalent stabilization. Despite a quarter century of intensive effort by a large number of laboratories, the orientation of the fundamental units in the gel is not known, nor, for that matter, is the arrangement of the subunit chains within the parent fibrinogen molecule. In this article some symmetry considerations are discussed in light of the geometry of the starting molecules and conditions necessitated by the covalent stitching which occurs after gel formation. Only a dimeric molecule in which the twofold symmetry axis coincides with a minor axis of an elongated fibrinogen molecule satisfies all the conditions.
P22 morphogenesis I: Catalytic scaffolding protein in capsid assembly
Authors: Casjens Sherwood , King Jonathan
Published: May 2005

About 250 molecules of the 42,000 molecular weight gene 8 product catalyze the polymerization of the major phage coat protein into a precursor shell temporarily containing both proteins. The resulting prohead appears to be a shell structure with the P8, or scaffolding protein, on the inside, and the coat protein on the outside. In concert with DNA condensation inside the shell, all 250 scaffolding molecules exit from the prohead, without proteolytic cleavage. These molecules then recycle and catalyze the formation of more proheads from newly synthesized coat protein. Such proteins, which catalyze assembly by temporarily associating with an intermediate stage, may represent a general mechanism of macromolecular assembly.
Phage head size determination and head protein cleavage in vitro
Authors: Pruss Gail , Barrett Kathleen , Lengyel Judith , Goldstein Richard , Calendar Richard
Published: May 2005

Satellite phage P4 causes the head proteins of a helper phage, such as P2, to form a small head. This small head is never found in cells infected by the helper virus alone. This finding, coupled with the dominance of P4 over its helper, indicates that the P4 genome has the potential for specific head size determination. Satellite phage P4 codes for a late protein which is found in the P4 head (45 copies/head). This protein may determine head size. Our finding that the small size of P4 DNA does not determine small head size in an in vitro DNA packaging system lends further support to the idea that a P4 protein determines small head size.

Formation of P2 headlike structures is accompanied by cleavage of P2 head proteins. Cleavage of the major head protein precursor can be observed in vitro after lysis of infected cells with lysozyme. The rate of this in vitro reaction is not affected by deoxyribonuclease; thus there cannot be a tight coupling between DNA packaging and the cleavage of the major capsid protein.
Binding properties of the plant photoreceptor phytochrome to membranes
Authors: Marmé Dieter
Published: May 2005

Phytochrome (P), a chromoprotein of 120,000 MW, occurs at low concentrations in all higher plants. The chromophore is an open tetrapyrrole. The pigment exists in two light‐absorbing forms: Pr, which absorbs at 660 nm, and Pfr, which absorbs at 730 nm. These forms are interconvertible by light. Pr, the physiologically inactive form, exists in dark‐grown plants; Pfr, the active form, appears after irradiation with red light, P‐mediated responses, of which about 80 are known, range from short‐time effects (sec) such as bioelectric potentials, to long‐time effects (hr) such as increases in enzymatic activity. Measurements of phototransformation in vivo with polarized light suggest that P is localized in the plasma membrane. Particulate cell fractions contain about 70% of total extractable P if Pfr is present and only 4% if Pr is present. Evidence indicates that the fraction containing Pfr may be the plasma membrane. One can isolate a partially solubilized membrane system, which can be reversibly reconstituted by adding Mg. The reformed vesicles bind Pfr in vitro. Pfr binding increases with decreasing pH and decreases with increasing monovalent cation concentration. Pfr is released from the membrane by far red light (Pr is formed) and by Triton X‐100. We suggest that Pfr binding to a membrane induces conformational changes; the functional properties of this membrane are altered, which might lead to the observed phytochrome‐mediated responses.
Oxidation of lipids and membranes I: In vitro formation of peroxidative lipid polymers
Authors: Wolman Moshe
Published: May 2005

Fluorescent polymers were obtained by oxidizing partly emulsified linolenic acid with different oxidants. The speed of formation of polymers differed for the various oxidants, and the difference was not a simple function of the oxidation potential. The speed of polymerization also depended on the nature of the emulsion.

The presence of egg albumen in the emulsion enhanced polymer formation with all oxidants. When the oxidants used are arranged in the order of decreasing speed of polymer formation, the order is different in the presence of albumen from what it is in the absence of albumen.

With different oxidation catalysts most antioxidants and amino acids tested enhanced polymerization. In oxidation with ferric ions, with K‐dichromate, and without added oxidants the only antioxidants which delayed polymerization were “inhibitors”. “Retarders” enhanced polymerization. With KMnO4 slight delay was caused by some retarders.

The findings indicate that not only oxidation catalysts, but also proteins, amino acids, and antioxidants enhance polymerization. The possibility is suggested that in animal cells lipid pigment formation might represent a mechanism for neutralizing free radicals.
Effect of crosslinking on mitochondrial structure and function
Authors: Tinberg Harold M. , Lee Calvin , Packer Lester
Published: May 2005

Rat liver mitochondria were treated with ethylacetimidate

Abbreviations: SDS, sodium dodecylsulfate; DMS, dimethylsuberimidate; EA, ethylacetimidate; MBI, methylbutyrimidate; TMPD, N, N′, N′‐tetramethyl‐p‐phenylenediamine.

and methylbutyrimidate, monofunctional imidates, and with dimethylsuberimidate, a bifunctional imidate, and the effects on structure and function studied. Mitochondria treated with 5 mM dimethylsuberimidate or greater did not respond osmotically when placed in deionized water. Sodium dodecylsulfate‐polyacrylamide gel electrophoresis revealed that at concentrations > 5 mM dimethylsuberimidate nearly all mitochondrial polypeptides failed to enter 6% gels, indicating crosslinking of both membrane and soluble proteins. Extensive amidination by ethylacetimidate and methylbutyrimidate had little effect on ascorbate‐tetramethylphenylenediamine oxidase while extensive inhibition resulted from dimethylsuberimidate treatment. The possible involvement of molecular motion in electron transport is discussed.
The possible role of tightly bound adenine nucleotides in oxidative and photosynthetic phosphorylation
Authors: Rosing J. , Harris D. A. , Slater E. C. , Kemp A.
Published: May 2005

The tightly bound nucleotides of the beef‐heart mitochondrial ATPase are released during cold inactivation followed by ammonium sulfate precipitation. During incubation at 0°C the sedimentation coefficient (s20 W) of the ATPase first declines from 12.1 S to 9 S. Prolonged incubation or precipitation with ammonium sulfate leads to dissociation of the 9 S component into subunits with s20 W of 3.5 S. The 9 S component still bears bound nucleotides which exchange more extensively and rapidly with added nucleotides than those bound to the active 12.1 S component. The bound nucleotides are lost when the 9 S form dissociates into the smaller subunits. Thus, firm binding of nucleotides is a property of the quarternary structure of the enzyme.

The exchangeability of the nucleotides bound to the ATPase of chloroplast membranes is greatly increased in membranes illuminated in the presence of pyocyanine. Pi can exchange into both the β and γ positions of the bound nucleotides when the membranes are energized in the presence of Mg2+. The exchange of the nucleotides and the incorporation of Pi are insensitive to the inhibitor Dio‐9 but are inhibited by the uncoupler S13.

Abbreviation: S13, 5‐chloro‐3‐t‐butyl‐2′‐chloro‐4′nitrosalicylanilide.

This inhibition by S13 parallels that of the inhibition of photosynthetic phosphorylation. These findings are discussed with regard to our hypothesis that electron transfer causes release of preformed tightly bound ATP from the ATPase by inducing a conformational change.
Crosslinking studies on the CA2+, MG2+‐activated ATPase of escherichia coli
Authors: Bragg Philip D.
Published: May 2005

Crosslinking of membrane proteins of Escherichia coli with dithiobis (succinimidyl propionate) (DSP) resulted in loss of several enzyme activities including the Ca2+, Mg2+‐activated ATPase. This enzyme was crosslinked by DSP to the membrane and was not released by dialysis at low ionic strength in the absence of dithiothreitol which could cleave the crosslinking group. DSP inactivated both phosphohydrolase and coupling activities of the solubilized ATPase. Loss of hydrolytic activity could be correlated with the extent of reaction of the α and/or β subunits of the enzyme. The loss of coupling activity appeared to be associated with modification of the γ and/or δ subunits.
Chemical and conformational events in regions of the myosin
Authors: Szent‐Györgyi Andrew G.
Published: May 2005

Structural changes in myosin may take place within the heavy chains, or may represent rearrangement of subunits. Changes induced by ATP and possibly restricted to the heavy chains are indicated by several different optical studies, including changes in absorbence of aromatic residues (1), changes in the fluorescene of dyes coupled to myosin (2), changes in electron spin resonance spectrum (3), and changes in the intrinsic fluorescence of tryptophan residues (4, 5). A calcium dependent subunit rearrangement in scallop myosin is indicated by fluorescene depolarization studies (Cheung and Szent‐Györgyi, unpublished observations). In scallop muscles, calcium regulates contraction by directly reacting with myosin (6), and the changes in the quaternary structure of myosin are likely to be related in the way calcium control works.

At first I will disucss the changes of fluorenscene that Drs. Weber, Fasman, and I have described several years ago (4). Then I will speculate on the implications of a subunit rearrangement on the mechanism of regulatory light chain funciton.
Does myosin‐substrate interaction in vitro result in a delocalized conformation change?
Authors: Cassim Joseph Y. , Lin Tsung‐I
Published: May 2005

The effect of substrate on the far UV (185–250 nm) and near UV (250–325 nm) circular dichroism (CD) of myosin and heavy meromyosin (HMM) was studied. The following results were obtained with the addition of ATP (during various conditions of hydrolysis), ADP, and pyrophosphate: (1) no changes were observed in the far UV CD, (2) ATP and ADP perturbed the near UV CD only at spectral regions below 280 nm coinciding with the regions of their optical activity, (3) the optically inactive pyrophosphate caused no change in the near UV CD, and (4) myosin and HMM gave exactly the same results. These results suggest that myosin‐substrate interaction in vitro does not result in a delocalized conformational change.
Hormone receptor mobility and catecholamine binding in membranes. A theoretical model
Authors: McGuire Robert F. , Barber Roger
Published: May 2005

[3 H]‐Catecholamine binding to intact cells, isolated cell membranes, and to several isolated macromolecules has been shown by several laboratories to be neither stereospecific nor inhibited by known β‐antagonists. Since additional evidence indicates that this binding is not an artifact (i.e. due neither to the binding of a catecholamine oxidation product nor hormone binding to a catabolic enzyme such as COMT), the question remains as to whether this represents binding to a bona fide membrane receptor. Because all ligands which bind strongly or compete for this binding possess a catechol group, one possible explanation is that the binding affinity is primarily determined by the catechol moiety, whereas the correct stereoisomer of the side chain is necessary to activate the receptor. Thus, although binding is a necessary condition for hormone action, the necessary and sufficient condition for activation of adenyl cyclase is both the catechol group and the correct stereoisomer of the side chain.

A theoretical model is developed here to provide a quantitative basis for this hypothesis. This model extends the current concept of distinct subunits in the adenyl cyclase system by separating the receptors from the catalytic sites and placing them at separate locations within the membrane. Utilizing the spare receptor model of Furchgott, and the mobility of macromolecules within a “lipid sea,” the appropriate equations to predict both hormone binding and enzyme activation are derived. Using the observed affinity constants from catecholamine binding studies, it is then shown that this model can predict the experimental observations and hence explain the apparent dichotomy arising from binding and enzyme activation studies.
Perturbation of the chemotactic tumbling of bacteria
Authors: Taylor Barry L. , Koshland D. E.
Published: May 2005

The bacterial sensing system has been studied on three levels. First, a quantitative method has been devised for measuring the “action spectrum” of the bacterium in response to a sudden addition of attractant. Second, a technique has been developed for the rapid isolation of mutants defective in the transmission part of the sensing system. Third, a study of the effects of light on the transmission system reveals two components, one which generates tumbling and another which inhibits it.
Transport of amino acids in intact 3T3 and SV3T3 cells. Binding activity for leucine in membrane preparations of ehrlich ascites tumor cells
Authors: Cecchini Gary , Lee Mary , Oxender Dale L.
Published: May 2005

Transport of amino acids into 3T3 and SV3T3 (SV40 virus‐transformed 3T3) cells was measured on glass cover slips. The 3T3 and SV3T3 cells contain both A (alanine preferring) and L (leucine preferring) systems for neutral amino acid transport. Initial rates of uptake of amino acids are about twofold higher in SV3T3 than in 3T3 cells. Other parameters measured, however, do not indicate marked differences in the transport of amino acids by the two cell types. L‐system amino acids, such as leucine, are subject to trans‐stimulation in both cell lines, whereas A‐system amino acids, such as alanine and glycine, are not. Leucine was transported to higher levels in confluent cells than in nonconfluent cells. Glycine, however, shows distinctly less transport activity as the cells become confluent.

Ehrlich ascites cell plasma membranes were prepared and assayed for amino acid‐binding activity. Leucine‐binding activity was detected by equilibrium dialysis in Triton X‐100‐treated membrane preparations.
Conjugated polyene fatty acids as fluorescent membrane probes: Model system studies
Authors: Sklar Larry A. , Hudson Bruce S. , Simoni Robert D.
Published: May 2005

The use of conjugated polyene fatty acids as probes of membrane structure is examined. α‐ and β‐parinaric acid (cis, trans, trans, cis‐ and all trans‐9,11,13,15‐octadecatetraenoic acid) and synthetic lecithins containing an α‐parinaric acid chai in position 2 have been prepared, and their absorption and fluorescence properties have been determined. Their absorption spectra are at sufficiently long wavelength to be unobscured by cellular chromophores such as nucleotides and aromatic amin acids. Parinaric acid absorption does, however, overlap tryptophan emission which allows fluorescence energy transfer.

Potential uses of these fluorescent probes are presented with studies on mode systems with known physical properties. Dipalmitoyl phosphatidylcholine exhibits a sharp phase transition 1° wide at 42° C, as monitored by the fluorescence intensit, of parinaric acid. The magnitude of the transition is independent of probe concentration, but the width of the transition and hysteresis are dependent upon such factors as the probe concentration and whether or not sonication is used in sample preparation. Using both fluorescence and absorption properties of the probe, we show that the addition of cholesterol to the dispersion broadens and decreases the magnitude of the transition. These results are interpreted in terms of a change in the polarizability of the acyl chains of a lipid bilayer as the bilayer undergoes a thermal transition.

Lipid‐protein interactions are studied by the binding of α‐parinaric acid to bovine serum albumin. Fluorescence enhancement, absorption spectral shifts, and quenching of tryptophan fluorescence are observed when α‐parinaric acid binds to bovine serum albumin. Calculations based on these measurements are consistent with two binding sites of KB ∼ 108 (M−1) and three to four binding sites of KB ∼ 106 – 107 (M−1), similar to known values for the binding of other long‐chain fatty acids.

Biosynthetic incorporation of β‐parinaric acid into the E. coli fatty acid auxotroph 30E βox− has been accomplished and phase transitions in cells and isolated phospholipids are shown.
The action of cytochalasin A on the in vitro polymerization of brain tubulin and muscle G‐actin
Authors: Himes Richard H. , Houston L. L.
Published: May 2005

The presence of cytochalasin A inhibits the self‐assembly of beef brain tubulin and rabbit muscle G‐actin in vitro and also decreases the colchicine binding of tubulin. Prior reaction of cytochalasin A with 2‐mercaptoethanol destroys its inhibitory effects. It is shown that cytochalasin A exerts its actions by reacting with sulfhydryl groups, possibly causing irreversible structural changes in the proteins. Cytochalasin B does not affect the tubulin assembly reaction.
Sarcomas routinely produced from putatively nontumorigenic Balb/3T3 and C3H/10T1/2 cells by subcutaneous inoculation attached to plastic platelets
Authors: Boone Charles W. , Jacobs Jerome B.
Published: May 2005

The Balb/3T3 and C3H/10T1/2 lines, noted for their marked postconfluence inhibition of proliferation and anchorage dependence, and frequently studied as nontumorigenic lines that are compared with tumorigenic sublines transformed with various agents, produced tumors within two to four months at low‐cell dosage (3 × 104 cells) when implanted subcutaneously attached to 1 × 5 × 10 mm polycarbonate platelets. Platelets alone did not produce tumors. The cultured Balb/3T3 tumor cells showed loss of both postconfluence inhibition of proliferation and anchorage dependence. Tumors arising form attached Balb/3T3 cells in (BALB/c × C57B1/6)F1 hybrids were shown to be transplantable to BALB/c but not to C57B1/6 mice, proving that the tumors were derived form Balb/3T3 and not from host cells. The tumors exhibited unique transplantation rejection antigens that did not cross‐react with each other. Scanning electronmicroscopy of Balb/3T3 cells and derive tumor cells on Teflon

Teflon: Registered trademark of DuPont Plastics.

substrates (on which only the tumor cells and not the parent Balb/3T3 cells could grow) revealed that the two cell types were remarkably similar in appearance, except that the tumor cells were larger and showed many more microvilli that tended to concentrate over the nucleus. We conclude that Balb/3T3 cells and C3H/10T1/2 cells are preneoplastic and give rise to spontaneously transformed clones when implanted in vivo attached to a solid substrate.
Molecular composition and origin of substrate‐attached material from normal and virus‐transformed cells
Authors: Culp Lloyd A.
Published: May 2005

The proteins and polysaccharides which are left adherent to the tissue culture substrate after EGTA‐mediated removal of normal, virus‐transformed, and revertant mouse cells (so‐called SAM, or substrate‐attached material), and which have been implicated in the cell‐substrate adhesion process, have been characterized by SDS‐PAGE and other types of analyses under various conditions of cell growth and attachment. The following components have been identified in SAM: 3 size classes of hyaluronate proteoglycans; glycoprotein Co (the LETS glycoprotein); protein Ca (a myosin‐like protein); protein Cb (MW 85,000); protein C1 (MW 56,000, which is apparently not tubulin); protein C2 (actin); proteins C3–C5 (histones) which are artifactually bound to the substrate as a result of EGTA‐mediated leaching from the cell; and proteins Cc, Cd, Ce, and Cf. The LETS glycoprotein (Co) and Cd appear in newly‐synthesized SAM (which is probably enriched in “footpad” material – “footpads” being focal areas of subsurface membranous contact with the substrate) in greater relative quantities than in the SAM accumulated over a long period of time (which is probably enriched in “footprint” material – remnants of footpads left behind as cells move across the substrate). Co and Cd turn over very rapidly following short radiolabeling periods during chase analysis. The SAM's deposited during a wide variety of cellular attachment and growth conditions contained the same components in similar relative proportions. This may indicate well‐controlled and coordinate deposition of a cell “surface” complex involving the hyaluronate proteoglycans, the LETS glycoprotein, actin‐containing microfilaments with associated proteins, and a limited number of additional proteins in the substrate adhesion site. Evidence indicates that SAM is the remnant of “footpad” vesicles by which the cell adheres to the substrate and that EGTA treatment weakens the subsurface cytoskeleton, allowing these footpad vesicles to be pinched off from the rest of the cell. Three different models of cell‐substrate adhesion are presented and discussed.