bluuebunny/crossref_metadata_2025_split huggingface dataset:
Surface‐enhanced Raman spectroscopic study of isomeric anisidines adsorbed on colloidal silver particles
Authors: Sarkar Uttam K. , Chakrabarti Subhasis , Misra T. N. 
Published: May 2005

AbstractSurface‐enhanced Raman scattering (SERS) spectra of o‐, m‐ and p‐anisidine molecules were compared with the solution Raman spectra. The experimental results suggest that the o‐ and m‐anisidine molecules are adsorbed on the metal surface principally through the nitrogen atom, whereas the p‐anisidine molecules are adsorbed through the π‐system of the phenyl ring. This observation is explained in terms of the electron densities on the N and O atoms and in the phenyl ring as reflected by the Hammett σ values of the isomers. Charge‐transfer interactions have been shown to contribute significantly to SERS.
Surface‐enhanced Raman scattering of triphenylmethane dyes on colloidal silver
Authors: Persaud Indira , Grossman William E. L. 
Published: May 2005

AbstractSurface Raman spectral studies of triphenylmethane dyes on colloidal silver were carried out. An assessment of the surface and solution spectra led to the conclusion that the dye molecules are most likely lying parallel to the surface of the sol and adopting C3 symmetry. The major vibrational changes suggest that the most important center of interaction is the central carbonium ion, since the greatest changes are observed for the vibrations of the central bonds and only small changes are observed for the N–phenyl stretching modes. For a fixed concentration of sol the lowest level of detection was 5 × 10−8 M.
Excitation profiles versus potential profiles in the determination of the charge‐transfer contribution to SERS of pyridine on a silver electrode
Authors: Kudelski A. , Bukowska J. 
Published: May 2005

AbstractThe relative SERS enhancement factors for pyridine adsorbed on a silver electrode were determined as a function of the laser wavelength and applied potential. The charge‐transfer (CT) contribution to the SERS intensity (I), Gct, was estimated from the excitation profiles (I vs. hv) and compared with the Gct values previously obtained from the I vs. electrode potential curves. A critical discussion of the determination of Gct with the aid of both methods is given.
Surface‐enhanced Raman scattering of CO2 dissolved in aqueous colloidal solutions of silver and gold
Authors: Kneipp Katrin , Wang Yang , Berger Andrew J. , Dasari Ramachandra R. , Feld Michael S. 
Published: May 2005

AbstractThe observation of surface‐enhanced Raman scatterings (SERS) from CO2 molecules dissolved in aqueous solutions of silver and gold colloids measured with 850 nm near‐IR excitation is reported. Different types of surface enhancement and surface‐enhanced Raman spectra were observed. The SERS spectrum of CO2 on colloidal gold is in good agreement with the spectrum of CO2 dissolved in water. Two different types of SERS spectra were found for CO2 on colloidal silver. They can be assigned to physisorbed and/or weakly chemisorbed CO2 molecules and to strongly bonded CO2 ‐ negatively charged surface radicals, respectively. The enhancement factor for the stretching mode of carbon dioxide is estimated to be of the order of 102−104, depending on the kinds of metal and types of adsorption, which demonstrates that SERS on colloidal silver or gold particles in solution offers possibilities for detecting CO2 dissolved in liquids at low concentrations.
Resonance Raman detection of two conformers for the cyanide adduct of cytochrome c peroxidase and their pH dependence
Authors: Rajani Cynthia , Kincaid James R. 
Published: May 2005

AbstractThe resonance Raman spectra of the adducts of cytochrome c peroxidase with four cyanide isotopomers (12C14N−, 13C14N−, 12C15N− and 13C15N−) are presented. The spectra reveal the presence of two conformers, an essentially linear conformer whose v(Fe—C) and δ(FeCN) modes occur at 445 cm−1 and 407 cm−1, respectively (at pH 10) and a bent conformer which exhibits two modes at 355 cm−1 and 445 cm−1 (at pH 10). At pH values below 7, the linear form v(Fe—C) shifts to ∼455 cm−1 in response to protonation of the distal histidyl imidazole (which strengthens the Fe—C bond). The stretching mode of the bent form experiences only a slight shift. This smaller shift of the bent form is consistent with the proposal that the bent form originates as a consequence of hydrogen bond formation with the off‐axis proton donor group of arginine (which is protonated at both pH values). The overall spectral response to pH changes reflects interactions with the bound ligand which may be important for heterolytic bond cleavage.
Raman study of the phase transition in LiTa0.9Nb0.1O3 single crystal
Authors: Ge Yun‐Cheng , Zhao Chao‐Zhong 
Published: May 2005

AbstractThe Raman spectra of LiTa0.9Nb0.1O3 single crystal were studied as a function of temperature between 300 and 1000 K. When heated above 900 K, the crystals transform from the ferroelectric phase to the paraelectric phase, and the Raman data suggest that the phase transition is second order. The softening of an A1 mode was observed, but the ‘soft mode’ hardened at 120 cm−1. The mechanism of the phase transition is likely to be of the order‐disorder type.
Dynamic rheological behavior of wheat glutens during heating
Authors: Hayta Mehmet , Schofield J David 
Published: May 2005

AbstractCreep and dynamic rheological tests indicated that addition of redox additives directly into gluten or into flour before gluten extraction resulted in differences in rheological parameters. Heating from 30 to 50 °C caused a decrease in elastic modulus whereas heating above 50 °C strengthened the structure as evidenced by an increase in elastic modulus. Higher elastic modulus and lower creep compliance values suggested that Hereward gluten was more highly cross‐linked than Riband gluten. Glutenin seemed to be affected more than gliadin during temperature sweep experiments. Both oxidising and reducing reagents showed similar weakening effects on gluten irrespective of addition into flour or gluten. Treatment with oxidising reagents, particularly bromate, slightly delayed the temperature for the increase in elastic modulus as assessed by temperature sweep experiments. The identical effect of reducing and oxidising reagents may be attributable to the differences in mode of action and intrinsic material properties. Copyright © 2005 Society of Chemical Industry
Surface glycosyltransferases on cultured mouse fibroblasts
Authors: Roth Stephen , Patteson Anne , White Diane 
Published: May 2005

AbstractPrevious work has suggested the presence of galactosyltransferases on the outer surface of the plasma membrane of a malignant and a nonmalignant cell line. This paper summarizes data indicating that three other classes of glycosyltransfeases are similarly located on cell surfaces. In addition to the original two cell lines examined, BALB/c 3T3 and BALB/c 3T12, two other lines of BALB/c origin have been investigated. These are the SV40–transformed 3T3 line and one of the revertants of the virally infected cells that is no longer malignant but retains a viral genome.
Assessment of physiological integrity of sonicated retinal rod membranes
Authors: Shichi Hitoshi , Shelton Emma 
Published: May 2005

AbstractAs the size of rod membrane fragments was reduced by sonication or by addition of the detergent Emulphogene, the intensity of the circular dichroism (CD) bands (210 and 221 nm) increased progressively with a blue shift in position. The intensity of the visible CD bands (340 and 495 nm) was also increased by sonication. Since the intensity increase of the CD bands was related to a reduction in turbidity, the anomalous CD features of intact membranes could be attributed to optical artifacts caused by the particulate nature of the material.Because the magnitude of the CD bands at 221 nm and 340 nm was essentially identical for the sonic suspension and detergent‐clarified solution, the adequacy of sonic suspensions can be assured by checking whether detergent affects the intensity of these bands.Suspensions of sonicated rod membranes, purified on Agarose, contained vesicles of 112 nm in average diameter. The morphology and size of the vesicles did not change upon photobleaching of rhodopsin. The vesicles retained such rod membrane properties as conformational insensitivity to photobleaching of the retinal chromophore, thermal stability, and pigment regenerability. Thus, the physiological integrity of rod membranes was maintained by the sonicated vesicles.From the most reliable estimate of the molecular ellipticity at 221 nm, the helical content of membrane‐bound rhodopsin was determined to be approximately 47%.
Characterization of the active transport of chlorotetracycline in Staphylococcus aureus by a florescence technique
Authors: Dockter Michael E. , Magnuson James A. 
Published: May 2005

AbstractThe antibiotic chlorotetracycline (CTC) is used as a fluorescent chelate probe to investigate its active transport in respiring Staphylococcus aureus cells. CTC chelation to magnesium or calcium leads to fluorescence enhancement. This enhancement is further increased when the polarity of its environment is decreased, as occurs when the complex moves from an aqueous environment into a membrane. Upon addition of CTC to a dispersion of S. aureus cells, a time dependent fluorescence enhancement is detected which is a monitor of the transport of the CTC‐divalent cation complex into the membrane. This uptake has been shown to be energy dependent and exhibits saturation kinetics with an apparent Km of 107 ± 20 μM by the same technique. The initial rates of antibiotic uptake are shown to have a pH optimum between 5.5 and 6.5. The effects of exogenously added EDTA and paramagnetic Mn2+ indicate that the CTC‐divalent cation complex is transported to the inside of the membrane. Exogenously added magnesium inhibits the accumulation process. This implies that the membrane CTC binding site involves a divalent cation sequestered away from the surface of the membrane, and only free CTC is bound to that site. The uptake of CTC is also temperature dependent with a maximal rate at 40°. Arrhenius plots of the initial fluorescence enhancement rates are found to be biphasic with a 27° transition temperature. The break in the plots presumably reflects an order‐disorder transition involving the fatty acids of the cell membrane. Thus, transport of the CTC involves movement through the fatty acid region of the membrane. This movement is facilitated by the more fluid state of the membrane above the transition temperature.
Accessibility of the carbohydrate moiety of membrane‐bound rhodopsin to enzymatic and chemical modification
Authors: Shaper Joel H. , Stryer Lubert 
Published: May 2005

AbstractGalactose was specifically inserted into the carbohydrate moiety of rhodopsin by incubating retinal disk membranes with UDP‐galactose: N‐acetylglucosamine galactosyltransferase. The stoichiometry of labeling ranged from 1.2 to 1.8 (average = 1.5) residues of galactose per molecule of rhodopsin, indicating that some or all of the oligosaccharide chains of membrane‐bound rhodopsin are readily accessible to enzymatic modification. These modified membranes were treated with galactose oxidase to generate an aldehyde at the C‐6 position of the inserted galactose units. The enzymatically‐oxidized membranes were then reacted with dansyl hydrazide to yield a fluorescent hydrazone which is sufficiently stable to permit spectroscopic analysis. This procedure for the specific attachment of a spectroscopic probe should be applicable to a wide variety of membrane glycoproteins.
Hormonal regulation of membrane phenotype
Authors: Carlson Sarah A. , Gelehrter Thomas D. 
Published: May 2005

AbstractIncubation of rat hepatoma cells (HTC) in tissue culture with glucocorticoids alters several membrane properties characteristic of transformed cells, without affecting the growth rate of these cells. Variant cell lines resistant to dexamethasone inhibition of plasminogen activator production have been isolated using an agar‐fibrin overlay technique to detect plasminogen activator production by individual colonies of HTC cells. The resistance to dexamethasone is not secondary to abnormal or absent glucocorticoid receptors, but due to a lesion in a later step in hormone action specific for plasminogen activator. These variants should prove useful for the study of the mechanism of steroid action as well as for the analysis of the role of proteases in the hormonal regulation of membrane function.
Active calcium transport via coupling between the enzymatic and the ionophoric sites of Ca2+ + Mg2+‐ATPase
Authors: Shamoo Adil E. , Scott Terrence L. , Ryan Thomas E. 
Published: May 2005

AbstractThe 20K dalton fragment of Ca2+ + Mg2+‐ATPase obtained from the tryptically digested sarcoplasmic reticulum has been further purified using Bio‐Gel P‐100. This removed low‐molecular‐weight UV‐absorbing and positive Lowry‐reacting contaminants. The ionophoric activity of the 20K fragment in both oxidized cholesterol and phosphatidylcholine: cholesterol membranes is unaltered by this further purification. The 20K selectivity sequence in phosphatidylcholine: cholesterol membranes is Ba2+ > Ca2+ > Sr2+ > Mn2+ Mg2+.Digestion of intact sarcoplasmic reticulum vesicles with trypsin, which results in the dissection of the hydrolytic site (30K) from the ionophoric site (20K), is shown to disrupt energy transduction between ATP hydrolysis and calcium transport. This further implicates the 20K dalton fragment as a calcium transport site.These data and previous evidence are discussed in terms of a proposed model for the ATPase molecular structure and the mechanism of cation transport in sarcoplasmic reticulum.
Energetics of galactose, proline, and glutamine transport in a cytochrome‐deficient mutant of salmonella typhimurium
Authors: Singh A. P. , Bragg P. D. 
Published: May 2005

AbstractThe effect of inhibitors and uncouplers on the osmotic shock‐sensitive transport systems for glutamine and galactose (by the β‐methyl galactoside permease) was compared to their effect on the osmotic shock‐resistant proline and galactose permease systems in cytochrome‐deficient cells of Salmonella typhimurium SASY28. Both osmotic shock‐sensitive and ‐resistant systems were sensitive to uncouplers and to inhibitors of the membrane‐bound Ca2+, Mg2+‐activated adenosine triphosphatase. This suggests that uptake by both types of systems is energized in these cells by an electrochemical gradient of protons formed by ATP hydrolysis through the ATPase.
Homogeneous antibodies directed against human cell surface antigens: I. The mouse spleen fragment culture response to T and B cell lines derived from the same individual
Authors: Lampson Lois A. , Royston Ivor , Levy Ronald 
Published: May 2005

AbstractThe use of the mouse spleen fragment culture system is extended to the production of antibodies to human lymphoblastoid cell lines. These antibodies were tested for reactivity against the immunizing cell line, and against a second cell line which had been derived from the same human blood sample. Many of the antibodies were found to discriminate between the 2 isogenic lines. These results demonstrate the potential of the mouse spleen fragment culture system to provide homogeneous reagents which detect distinguishing markers on closely related human cells.
Chemical and immunological studies of cell surfaces from normal and transformed cells
Authors: Grimes W. J. , Van Nest Gary A. , Kamm Arthur R. 
Published: May 2005

AbstractImmunological and chemical studies of cell surfaces from normal and transformed BALB/c fibroblasts have shown alterations associated with transformation. The cells studied include normal lines which do not cause tumors when injected into BALB/c mice, viral transformants, and spontaneous transformants which cause tumors that either regress or grow progressively, killing the host. The spontaneously transformed progressors include cell lines which are immunogenic and nonimmunogenic as determined by the ability of tumor excision to protect an animal from subsequent rechallenge by tumor cells. Tumor‐bearing mice produce lymphocytes which are nonspecifically cytotoxic for all the normal and transformed lines. Some of the cell lines induce specific antibody formation in BALB/c hosts. Antisera have been prepared in rabbits which are specific for the transformed cell lines. These antisera can be used to determine specific surface changes on the transformed cells. Chemical studies have shown glycolipid alterations between the normal cells and some, but not all, of the transformants. Glycoproteins labeled by lactoperoxidase‐125 I or [3H] glucosamine were compared by SDS gel electrophoresis. Results from these studies do not show changes associated with malignancy. Individual glycoprotein regions from gels were treated with pronase, and the glycopeptides compared by Sephadex G‐50 chromatography. Alterations in glycopeptides from several cellular glycoproteins are the only changes which appear to be associated with malignancy.
Lectin affinity chromatography of cell surface proteins of novikoff tumor cells
Authors: Glenney John R. , Walborg Earl F. 
Published: May 2005

AbstractNovikoff hepatocellular carcinoma cells were radioiodinated by a cell surface‐specific method using lactoperoxid ase/125I. The iodinated proteins were solubilized in 0.5% Nonidet P‐40 and subjected to affinity chromatography on Sepharose‐conjugated lectins (Ricinus communis agglutinins I or II, soybean agglutinin, concanavalin A, or wheat germ agglutinin) and analyzed by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. Almost all the iodinated proteins bound to one or more of the Sepharose‐conjugated lectins, presumptive evidence that these peptides are glycosylated. Lectin affinity chromatography resolved defined subsets of iodinated glycoproteins and suggested that certain glycoproteins could be fractionated on the basis of heterogeneity of their heterosaccharide moieties. Incubation of the iodinated cells with neuraminidase resulted in increased binding of iodinated proteins to Sepharose‐conjugated Ricinus communis agglutinins I and II and soybean agglutinin and decreased binding to Sepharose‐conjugated wheat germ agglutinin. Binding of iodinated proteins to concanavalin A was unaffected by neuraminidase treatment of the cells. These studies demonstrate the utility of lectins for the multicomponent analysis of plasma membrane proteins.
Growth control of normal and transformed cells
Authors: Riddle Veronica G. H. , Pardee Arthur B. , Rossow Peter W. 
Published: May 2005

AbstractBoth serum factors and protein synthesis are required for normal cell growth. Swiss 3T3 cells require the serum growth factors insulin and EGF (epidermal growth factor) during the initial part of the G1 period, until they pass a restriction point about 2 h before the initiation of DNA synthesis. Concentration of cycloheximide that inhibit protein synthesis by as much as 70% dramatically lengthen the cell cycle before the restriction point, while the cell cycle after the restriction point remains nearly constant. These results are consistent with a model in which labile proteins are required for transit of cells past the serum‐sensitive restriction point. The relation of these findings to the growth control of transformed cells is discussed.
Tumorigenicity of revertants from an SV40‐transformed line
Authors: Steinberg Bettie M. , Rifkin Daniel , Shin Seung‐il , Boone Charles , Pollack Robert 
Published: May 2005

AbstractA syndrome of in vitro properties correlates with the tumorigenicity of SV40‐transformed rodent cells. These properties are plasminogen activator production, loss of large actin cables, and anchorage‐independent growth. An established rat fibroblast line, its SV40 transformant, several T‐antigen negative revertants, and a spontaneous retransformant isolated form one of the revertants were analyzed in vivo for their tumorigenicity and in vitro for the syndrome. The two transformed lines were highly tumorigenic, and had clearly abnormal in vitro properties. The parental rat line was weakly tumorigenic in nude mice and demonstrated a slightly transformed response in the in vitro assays. The revertants were completely nontumorigenic. Expression of the in vitro syndrome was not uniform for all revertants; however, most cell lines maintained the correlation of the syndrome and tumorigenicity.
Averages of glutamine synthetase molecules as obtained with various stain and electron dose conditions
Authors: Kessel M. , Frank J. , Goldfarb W. 
Published: May 2005

AbstractAveraged projections of individual glutamine synthetase molecules have been obtained by using electron microscopy and image processing. The methodology of correlation averaging under low dose conditions is described in detail. Because of their low signal‐to‐noise ratio, images made under low dose conditions cannot be directly interpreted in terms of high resolution features. Computer averaging of these images reveals a division of the subunit projection into two domains whose sizes agree with results of Lei et al [2] limited proteolysis experiments.
Developmental regulation of glycoprotein biosynthesis in dictyostelium
Authors: Ivatt Raymond J. , Das O. Prem , Henderson Ellen J. , Robbins Phillips W. 
Published: May 2005

AbstractWe have examined the glycoprotein‐linked oligosaccharides assembled during the life cycle of Dictyostelium discoideum, and found their expression to be dramatically dependent upon the stage of development. During early development mature glycans have a high mannose character, and a substantial proportion acquire a fucose residue that correlates with endo‐H resistance. One‐third of the glycans also acquire sulfate residues. These glycans diminish in importance during aggregation.The mature glycans expressed during late development contain fewer mannose residues, from five to ten mannose residues, and are characterized by the absence of sulfate residues and by the presence of fucose residues on endo‐H‐sensitive glycans. These glycans make their appearance coincident with the construction of tips on tight cell mounds. At this stage glycans characteristic of both early and late stages occur simultaneously.Developmental regulation of the wide array of protein‐linked glycans expressed during the life cycle of Dictyostelium discoideum may be as simple as the controlled transition from a group of structures that are assembled by the vegetative cells to a group of structures that are assembled by the terminally differentiating cells. The potential biological significance of this transition is discussed.
Long‐term epidermal growth factor–receptor internalization and processing in quiescent human fibroblasts
Authors: King A. Christie , Cuatrecasas Pedro 
Published: May 2005

AbstractEpidermal growth factor is internalized into cells and concomitantly induces a massive clearance of up to 90% of its total surface receptors. The hormone‐receptor complex is delivered to lysosomes and degraded or inactivated. Lysosomotropic alkylamines block the degradation but not the binding‐or internalization of ligand‐receptor complexes and thus their presence results in a marked potentiation of intracellular accumulation of epidermal growth factor. We have used these alkylamines as pharmacological tools to trap internalized 125I‐labeled epidermal growth factor and now report that the residual population of epidermal growth factor receptors remaining on human fibroblasts after completion of the receptor clearance process is not only accessible for ligand binding but also directs the continued internalization and degradation of this growth factor over prolonged periods of time. We also show that down regulation of epidermal growth factor receptors does not result in desensitization of cells to the mitogenic response.