bluuebunny/crossref_metadata_2025_split huggingface dataset:
Crossing of anisotropic and isotropic Raman components in the intermolecular resonance coupling of vibrations III‐Ca(ClO4)2 and benzene solutions in acetone
Authors: Kęcki Zbigniew , Sokolowska Anna 
Published: May 2005

AbstractChanges in the wavenumbers of the anisotropic and isotropic components of the C=O stretching band in the Raman spectrum of Ca(ClO4)2 and benzene solutions in acetone were investigated. Non‐coincidence values defined as Δv = vaniso — viso for the C = O band in Ca(ClO4)2 solutions were positive (+ 5 cm−1) for bulk acetone and negative (—25 cm−1) for acetone‐shared ion pairs. In acetone solutions diluted with benzene there is a decrease in C = O non‐coincidence from +5 cm−1 down to about — 1 cm−1. The change of non‐coincidence sign appears at a benzene/acetone molar ratio of 10. The concept of third‐body mediation is applied to explain the observed changes of non‐coincidence in highly polar and non‐polar diluents.
Frequency dependence of the polarizability derivative [∂α(ω)/∂r]o of chlorine from temperature‐dependent gas‐phase refractive index measurements
Authors: Hohm Uwe , Trümper Ulf 
Published: May 2005

AbstractThe refractive index n(ω, T, p) of molecular chlorine, Cl2, was measured in the ranges of temperature T between 290 and 1100 K and pressure p between 104 and 2 × 105 Pa and at three wavelengths λ = 2μco/ω between 632.990 and 543.516 nm. From these measurements the frequency and temperature dependence of the mean dipole polarizability < α(ω)T of Cl2 was obtained. The polarizabilities were analysed according to theories of Bell and Buckingham, yielding 1020[∂α(ω)/∂r]o/m2 = 2.02(22) + 6.27(51) × 10−32 (ω/s−1)2 for the frequency dependence of the polarizability derivative of chlorine between ω = 0 and 3.5 × 1015 s−1. This result is in fair agreement with ab initio calculations, but disagrees with polarizability derivatives obtained from measurements of the differential Raman scattering cross‐section.
SERS of 1,8‐naphthyridine and the Raman spectra of two of its complexes
Authors: Griffith William P. , Koh Tse Yuen 
Published: May 2005

AbstractThe surface‐enhanced Raman (SER) spectra of 1,8‐naphthyridine (napy) adsorbed on silver colloids were measured. An edge‐on configuration for the molecule is suggested, based on a comparison of the SER spectra of napy compared with the conventional Raman spectra of two of its complexes, Ag2,(μ‐napy)2(NO3)2 and OsO4 (napy), the former serving as a model for an edge‐on configuration of napy.
Magnetic resonance studies on membrane and model membrane systems: II. Phosphorus spectra and relaxation rates in dispersions of lecithin
Authors: Horwitz Alan F. , Klein Melvin P. 
Published: May 2005

AbstractWe present phosphorus magnetic resonance (PhMR) spectra, relaxation rates, and chemical shifts for unsonicated and sonicated lecithins in aqueous dispersions and for egg lecithin in chloroform and methanol. Aqueous lecithin dispersions are characterized by long values for T1 and considerably shorter values for T2. Both of these values as well as the value of the linewidth change with sonication. Lecithin dispersions in methanol and chloroform have relaxation rates shorter than those seen for sonicated lecithin. We do not, at this time, present a detailed interpretation of these results. On an empirical level, however, since the relaxation rates are sensitive to the type of dispersion and possibly to the solvent, we are optimistic that they will be sensitive to structural changes involving the headgroup region.
Derepressed leucine transport activity in Escherichia coli
Authors: Rahmanian Mohamad , Oxender Dale L. 
Published: May 2005

AbstractTransport activity and synthesis of binding protein for the amino acids leucine, isoleucine and valine in E. coli are coordinately controlled by the level of leucine in the growth medium. Spontaneous mutants (dlu) which can utilize D‐leucine as a source of L‐leucine show derepressed transport activity for the three‐branched chain amino acids. The increased transport activity is a result of an increase in the binding protein for these amino acids. Azaleucine‐resistant mutants have been isolated which have a defect in leucine transport but normal levels of the binding protein for leucine.
A rapid method for determining the topological distribution of anionic sites on membrane surfaces
Authors: Nicolson Garth L. 
Published: May 2005

AbstractA method is described for the topological localization of cell surface anionic sites using positively charged colloidal iron hydroxide (Gasic et al., Lab. Invest. 18, 63 [1968]). Purified glutaraldehyde‐fixed plasma cell membranes or glutaraldehyde‐fixed lysed cells are mounted on thin support films and directly stained with colloidal iron at pH 1.8, washed, dried, and then examined by transmission electron microscopy. Using this method the surface anionic residues on rabbit erythrocytes and murine MOPC‐70A myeloma cells are presently in randomly spaced clusters. The distribution of anionic residues on rabbit spermatozoa is discontinuous: the sperm tails almost exclusively bind the colloidal iron in a dense random distribution, while the heads show little or no labeling.
Processing and assembly of the head of bacteriophage lambda
Authors: Kaiser Dale , Syvanen Michael , Masuda Terrie 
Published: May 2005

AbstractWhen phage DNA is added to an extract of an induced lambda lysogen, complete phage particles are made that contain the added DNA. The DNA substrate for packaging is a covalently joined polymer of several phage units. Unjoined units must first be joined by DNA ligase in the extract. Therefore DNA cutting is a necessary part of the DNA packaging reaction. The protein product of gene A, called A protein, behaves like the enzyme that cuts DNA and is a necessary component of the extract.Three of the head proteins preassemble into a spherical shell that subsequently combines with DNA. These shells are made of E protein, the major protein of a finished head, and they can be the sole source of that protein. They also contain a few molecules of two processed proteins, fused C–E and cleaved B. The processing may be essential for assembly because other shells that contain C protein not fused and B protein uncleaved are less than 1% as active.Protein A and DNA first react with the protein shells, then D protein, the second most abundant head protein, is added. These new observations are combined with published data to develop a comprehensive view of λ head assembly.
Assembly of salmonella flagellin in vitro and in vivo
Authors: Lino Tetsuo 
Published: May 2005

AbstractFormation of a flagellar filament of Salmonella from its component protein, flagellin, is in principle a self‐assembly process, which proceeds by the addition of flagellin monomers one by one to the distal end of the filament. Upon their polymerization, a conformational change of flagellin molecules occurs, and it confers polarity to the filament. For the initiation of in vitro flagellin assembly in a solution of physiological ionic strength and pH, it is essential to add fragments of flagellar filaments, which work as seeds for the polymerization of flagellin monomers. When an appropriate concentration of some anion known as a good salting‐outer is added to the solution, the polymerization begins without addition of seed. Assembly of flagellins in vivo begins at the distal end of each hook. The distal ends of the hooks on the cells of a flagellin‐less mutant were shown to initiate the assembly of exogenous flagellin in vitro, although the efficiency was not as high as that of the in vivo initiation. A flagellar filament elongates in vitro at a constant rate as long as a sufficient amount of flagellin is supplied, and the elongation terminates by an error occurring at the growing end of the filament. On the contrary, the rate of in vivo elongation decreases exponentially with increase of the length of the filament. Initial rate of the in vivo elongation depends on growth condition of the bacteria, while decrease of the rate per unit filament length is little affected by the growth condition. The observed limit in length of the flagellar filaments on growing bacteria is expected from the exponential decrease of their rate of elongation. The decrease of the in vivo elongation is correlated with the lowering of the transportation efficiency of flagellin monomers on their passage from the cell body through the central canal of a flagellar filament to the tip.
Endocytosis and exocytosis: Role of microfilaments and involvement of phospholipids in membrane fusion
Authors: Korn Edward D. , Bowers Blair , Batzri Shmuel , Simmons Susan R. , Victoria Edward J. 
Published: May 2005

AbstractA brief description of endocytosis and exocytosis is followed by a discussion of the experimental approaches to the study of the initial events of endocytosis, the possible involvement of microfilaments, and in particular the possible role of membrane lipids in the events of membrane fusion. Recently developed model systems are also discussed.
Birefringence changes in vertebrate striated muscle
Authors: Taylor D. Lansing 
Published: May 2005

AbstractThe changes in birefringence in the rigor to relax transition of single Triton‐extracted rabbit psoas muscle fibers have been investigated. The total birefringence of rigor muscle fibers was dependent on sarcomere length and ranged from (1.46 ± 0.08) × 10−3 to (1.60 ± 0.06) ± 10−3 at sarcomere lengths from 2.70 μm to 3.40 μm. An increase in total birefringence was measured dependent on sarcomere length when 55 single fibers were relaxed from the rigor state with Mg‐ATP. Pyrophosphate relaxation produced a smaller increase in retardation when compared to Mg‐ATP. The expected change in intrinsic birefringence during the rigor to relax transition was calculated assuming a hinge function of the subfragment 2 moiety of myosin. The changes in birefringence during isometric contraction and relaxation have been discussed in relation to possible structural changes.
Interaction of homogeneous mitochondrial ATPase from rat liver with adenine nucleotides and inorganic phosphate
Authors: Pedersen Peter L. 
Published: May 2005

AbstractMitochondrial ATPase from rat liver mitochondria contains multiple nucleotide binding sites. At low concentrations ADP binds with high affinity (1 mole/mole ATPase, KD = 1–2 μM). At high concentrations, ADP inhibits ATP hydrolysis presumably by competing with ATP for the active site (KI = 240–300 μM). As isolated, mitochondrial ATPase contains between 0.6 and 2.5 moles ATP/mole ATPase. This “tightly bound” ATP can be removed by repeated precipitations with ammonium sulfate without altering hydrolytic activity of the enzyme. However, the ATP‐depleted enzyme must be redissolved in high concentrations of phosphate to retain activity. AMP‐PNP (adenylyl imidodiphosphate) replaces tightly bound ATP removed from the enzyme and inhibits ATP hydrolysis. AMP‐PNP has little effect on high affinity binding of ADP. Kinetic studies of ATP hydrolysis reveal hyperbolic velocity vs. ATP plots, provided assays are done in bicarbonate buffer or buffers containing high concentrations of phosphate. Taken together, these studies indicate that sites on the enzyme not directly associated with ATP hydrolysis bind ATP or ADP, and that in the absence of bound nucleotide, Pi can maintain the active form of the enzyme.
Purification and properties of membrane‐bound coupling factor‐latent ATPase from mycobacterium phlei
Authors: Kalra Vijay K. , Lee Soon‐Ho , Ritz Carolyn J. , Brodie Arnold F. 
Published: May 2005

AbstractThe membrane bound coupling factor‐latent ATPase was solubilized from the membrane vesicles of Mycobacterium phlei by using 0.25 M sucrose or low ionic strength buffer. Purification of the solubilized enzyme by use of Sepharose‐ADP conjugate gel yielded a homogenous preparation of latent ATPase which was purified about 216‐fold in a single step with an 84% yield. The enzyme exhibits a specific activity of 39 μmoles of ATP hydrolyzed per min per mg protein. The purified enzyme exhibits coupling factor activity. Electrophoresis in two dissociating solvent systems indicates that the enzyme contains at least three major polypeptides of molecular weights 56,000, 51,000 and 46,000 daltons, and two minor polypeptides of 30,000 and 17,000 daltons. Equilibrium binding studies of ADP with purified coupling factor‐latent ATPase reveal the presence of two nucleotide binding sites per molecule with an apparent Ka of 8.1 × 10−5 M.By use of affinity chromatography, another latent ATPase has been isolated from the solubilized enzyme, which does not exhibit coupling factor activity.
Cell surface receptors and their dynamics on toxin‐treated malignant cells
Authors: Nicolson Garth L. , Robbins James C. , Hyman Robert 
Published: May 2005

AbstractThe binding, mobility, and mode of cell entry of the plant toxin ricin (or RCAII) were investigated on susceptible and partially resistant murine cell lines. When susceptible cells (SV40‐transformed 3T3 fibroblast cells and BW5147 lymphoma cells) were examined, ricin bound rapidly, induced endocytosis, and entered the cell cytoplasm via broken endocytotic vesicles to inhibit cell protein synthesis, as found previously (1). Addition of lactose within 15 min after initial ricin binding prevented toxicity. After this time lactose addition no longer blocked the inhibition of protein synthesis.In a partially resistant lymphoma (BW5147/RCA3) that shows only a slight reduction in the total number of ricin‐binding sites, ricin bound rapidly to the cell surface, but was endocytosed significantly less at low ricin doses compared to its parental line, indicating a possible difference in cell surface behavior. The exposed surface proteins on the BW5147 parental and BW5147/RCA3 resistant lines were examined by 125I‐labeling utilizing lactoperoxidase‐catalyzed iodination. The radiolabeled components were solubilized and separated by slab gel electrophoresis in sodium dodecyl sulfate. Autoradiograms of the slab gels indicated that two surface components of approximately 80,000 and 35,000 mol wt were much less exposed or were missing on the resistant line.
Binding of agonists and antagonists to muscarinic receptors
Authors: Birdsall N. J. M. , Burgen A. S. V. , Hiley C. R. , Hulme E. C. 
Published: May 2005

AbstractThe binding of one irreversible and two reversible radioactive antagonists to muscarinic receptors in synaptosome preparations of rat cerebral cortex has been studied. The ligands all bind to the same receptor pool and directly and competitively yield self‐consistent binding constants closely similar to those obtained by pharmacological methods on intact smooth muscle. The binding process for antagonists seems to be a simple mass action‐determined process with a Hill slope of 1.0. The quantitative correlations strongly support the view that the receptor studied by ligand binding corresponds to the receptor studied by pharmacological methods.Inhibition of antagonist binding by most agonists shows a reduced Hill slope which also applies to direct binding studies of [3H] acetylcholine. Mechanisms that might account for the behavior of agonists are discussed but do not conclusively point to any single mechanism.
Appearance of acetylcholine receptors in cultured myoblasts prior to fusion
Authors: Teng Nelson N. H. , Fiszman Marc Y. 
Published: May 2005

AbstractThe development of the acetycholine receptors in chick embryo myoblasts from 11‐day old embryos was studied in vitro. Using the purified α‐bungarotoxin labeled with radioactive iodide, a high concentration of acetylcholine receptors was found in the prefusing myoblasts; most of these receptors were located in the interior of the myoblasts. However, upon the completion of myoblast fusion, the majority of the acetylcholine receptors appeared on the external cell surface of the myotubes.
The existence of a group translocation transport mechanism in animal cells: Uptake of the ribose moiety of inosine
Authors: Quinlan Dennis C. , Li Chien‐Chung , Hochstadt Joy 
Published: May 2005

AbstractAfter exposure to inosine, transport‐competent plasma membrane vesicles isolated from SV ‐40‐transformed Balb/c 3T3 cells accumulate intravesicular ribose 1‐PO4 at a concentration 200‐fold greater than the extravesicular concentration. An analysis of the purine nucleoside phosphorylase activity distribution in various subcellular fractions, relative to other enzyme activities, indicated the presence of plasma membrane‐associated purine nucleoside phosphorylase activity. The plasma membrane vesicles appear relatively impermeable to hypoxanthine. However, hypoxanthine, which is a competitive inhibitor of the transport reaction, is the only compound tested capable of mediating efflux of already accumulated ribose 1‐PO4. In addition, hypoxanthine does not result in the efflux of transported uridine which is accumulated in these membrane vesicles as uridine. Exogenous ribose 1‐PO4 neither results in counterflow nor does it inhibit the original uptake reaction. The following transport reaction is proposed: uptake occurs by group translocation, mediated by membrane‐localized purine nuceloside phosphorylase. The data are consistent with sites for inosine and hypoxanthine being on the outer membrane surface whereas the ribose 1‐PO4 site is only on the inner surface.
The correlation of plasma membrane microvilli and intracellular cyclic AMP content in a rat epitheloid kidney cell line
Authors: Carley William W. , Moses Harold L. , Mitchell William M. 
Published: May 2005

AbstractModulation of the intracellular concentration of cyclic AMP has been associated with a regulatory role in cell division, cell morphology, and physical properties of the plasma membrane. Untransformed rat kidney cells in culture exhibit epitheloid morphology, high intracellular cyclic AMP levels, and contact inhibition of growth. Untransformed rat kidney cells transformed with the Kirsten murine sarcoma virus exhibit a low cyclic AMP content, rapid growth rate, and a loss of contact inhibition. Scanning electron microscopy reveals a distinctive difference in the surface structure of the two cell types during G1 of the cell cycle. The surface of the transformed cell is covered with microvilli while its untransformed counterpart is devoid of microvilli. The presence of microvilli can be controlled as a function of temperature by two temperature‐sensitive mutants of the Kirsten sarcoma virus (ts6t6 and ts371 cl 5). In the ts6t6 mutant, growth at 32°C results in a low cyclic AMP content and the presence of microvilli, while growth at 39°C results in a high cyclic AMP content and a decrease in microvilli. The oposite effect is seen with the ts371 cl 5 mutant. Correlation of cyclic AMP content with the presence of microvilli suggests that this surface phenomenon is a function of cyclic AMP concentration.
Central nervous system antigen (NS‐5) and its presence during murine ontogenesis
Authors: Zimmermann Astrid , Schachner Melitta , Press Joan L. 
Published: May 2005

AbstractAn antiserum raised by immunization of C3H.SW/Sn mice with cerebellum from 4‐day‐old C57BL/6J mice recognizes a cell surface component(s) [NS‐5] present in different degrees on various parts of the mouse central nervous system. When analyzed by an antiserum‐and complement‐mediated cell cytotoxicity test and by the ability of various tissues to absorb anti‐NS‐5 antiserum activity, the antigen(s) was detectable on cerebellum, retina, olfactory bulb, cortex, basal ganglia, and medulla, but not on nonneural tissues with the exception of mature spermatozoa and 4‐day‐old kidney. The antigen(s) detected by the anti‐NS‐5 antiserum was found in similar quantities on young and adult rat and mouse cerebellum; however, it was not detectable on any of 16 clonal cell lines derived from the rat central nervous system. During preimplantation stages of murine development, the antigen could be detected on all cells of (2–4)‐cell and (8–16)‐cell stages and on the trophoblastic cells of blastocysts by indirect immunoflourescence. Embryos on day 9 of gestation, the earliest stage tested after implantation, expressed the antigen(s), but expression was restricted to the nervous system.
Pyruvate‐Induced changes in hepatoma cell morphology and macromolecular synthesis
Authors: Pickart L. , Thaler M. Michael 
Published: May 2005

AbstractCells maintained in basal growth medium with 0.2–1.0% serum often require citric acid cycle intermediates for optimal viability. We have found that pyruvate added to minimal growth medium causes cellular flattening and formation of external processes accompanied by increaded DNA synthesis in cultured hepatoma cells (HTC cells).Cells were cultured in plalstic T‐flasks (0.5, 1.0, or 2.0 × 106 cells/flask) containing 5 ml medium (90% Eagle's Basal Medium (BME) and 10% Swim's S‐77) with various concentrations of fetal calf serum (0.2,0.25, 0.5, 1.0, 2.0, 10%) and either pyruvate (50, 100, 250,500, 1,000μg/ml), or one of: dibutyryl cAMP (DBcAMP) or dibutyryl cGMP (DBcGMP) at 10−3, 10−4, or 10−5 M. At 44–48 hr cultures were pulsed with tritiated thymidine, uridine, or lecucine. Cells became attached to the plastic surface within 24hr. Cells in medium with 0.25 to 2.0% serum had a rounded appearance. With added pyruvate, cellular flattening, process formation, and an increased adherence to the substratum was absorbed. By 48 hr, culture without pyruvate grew in rounded clusters; with pyruvate, cells formed extensive interconnecting processes that appeared loosely attached to the monolayer surface. At the cell densities tested, process formation was maximal with 250 to 500 μg/ml pyruvate. Cytochalasin B blocked flattening and process formation; EDTA (1 mg/ml) caused retraction of processes within 3 min, and a slow dissolution of these structures within cells was observed. DBcAMP or DBcGMP did not induce process formation. Flattening and process foormation in pyruvate‐enriched cultures were accompanied by marked stimulation of DNA synthesis and smaller increases in RNA and protein synthesis. Cell number was not affected.These pyruvate‐induced changes suggest that alterations in energy metabolism, or precursors that enhance viability and macromolecular synthesis in mammalian cell cultures, may exert marked effects on cellular morphology without corresponding changes in growth of neoplastic liver cells.