bluuebunny/crossref_metadata_2025 huggingface dataset:
Analyse Vibrationnelle et Structurale en Série Aliphatique Saturée. X—Spectres de Vibration de l'Acide Adipique et de ses Sels Alcalins de Potassium en Solution Aqueuse
Authors: Ramsis H. , Monmouton P. , Delarbre J. L. , Maury Et L.
Published: May 2005

Les spectres infrarouge et Raman de l'acide adipique et de ses sels de potassium en solution aqueuse ont été analysés. Une attribution des fréquences fondamentales est proposée. L'analyse de l'état de polarisation des raies Raman montre que les deux sels appartiennent au groupe de symétrie Cs tandis que l'acide répond au groupe de symétrie C1. A l'état cristallin, le sel acide est de type A selon la classification de Speakmann. Une comparaison des conformations avec celles déterminées en série alcanedioique a été réalisée.
Dispersion of the oblique phonons in tetragonal BaTiO3 and Ce: BaTiO3
Authors: Wang Rong‐Ping , Jiang Yi‐Jian , Zeng Ling‐Zhi , Liu Yu‐Long , Zhu Yong
Published: May 2005

Raman spectra of oblique phonons in tetragonal BaTiO3 and Ce : BaTiO3 single crystals were obtained for different values of the angle θ which the phonon wavenumber q̄ makes with the c‐axis. On the basis of Merten's equation, the directional dispersion curves were fitted and plotted. The results show that the A1(TO) phonons of BaTiO3 at 275 and 514 cm−1 come from first‐order scattering, which is evidence for the order—disorder model of the ferroelectric phase transition. The Raman spectra of Ce : BaTiO3 are reported for the first time and the results indicate that Ce atoms have little effect on the structure of BaTiO3.
Molecular reorientation in liquid acetonitrile studied by depolarized light scattering experiments
Authors: Giorgini M. G. , Morresi A. , Mariani L. , Cataliotti R. S.
Published: May 2005

Time correlation functions from depolarized light scattering experiments at several temperatures were examined by biexponentials that simultaneously account for the unique axis molecular reorientations (on the picosecond time‐scale) and collisional processes (on the subpicosecond time‐scale). The first are found to be systematically slower than those obtained in previous studies. The important role played by dipolar interactions on the molecular organization in the liquid is confirmed. Comparison with dieletric relaxation times indicates that rotational diffusion provides only an approximate description of molecular reorientation in liquid acetonitrile. Application of the J‐diffusion model shows that the exponential decay of the observed orientational correlation functions cannot be taken as evidence of rotational diffusion in liquid acetonitrile.
High‐resolution coherent anti‐stokes Raman spectroscopy of ethane
Authors: Bican T. H. S. , Jonuscheit J. , Lehner U. , Schrötter H. W.
Published: May 2005

A continuous‐wave CARS spectrometer was equipped with a new frequency‐stabilized argon ion ring laser and better stabilization for the tunable dye laser was introduced. Special quartz sample cells with Brewster angle windows were placed in the focal region of the argon ion ring laser. A new data acquisition system was installed which allows the simultaneous recording of CARS signals and calibration spectra and the subsequent evaluation of the data. An instrumental resolution of less than 0.001 cm−1 and a wavenumber accuracy of about ± 0.006 cm−1 were achieved. As an example of the performance of the spectrometer, the CARS spectrum of ethane was measured in the region of the CH vibrations at pressures between 95 and 1.9 kPa. The spectra were compared with the stimulated Raman spectrum published recently.
Application of continuous extended scanning techniques to the simultaneous detection of Raman scattering and photoluminescence from calcium disilicates using visible and near‐infrared excitation
Authors: Dyer Chris , Smith Brian J. E.
Published: May 2005

A novel method of data acquisition is described for spectrographs employing charge‐coupled device (CCD) detection. The technique, called continuous extended (CE) scanning, allows data collection over the full spectral range of the spectrograph, rather than a limited window determined by the wavelength, spectral dispersion, spectrograph focal length and detector dimensions. The CE method removes the need to sacrifice resolution for spectral range or the need to record and splice many spectral segments to reproduce a full‐range spectrum. The advantages of this method are discussed and the capability is demonstrated with respect to several calcium disilicate minerals, recently shown to exhibit intriguing behaviour under near‐infrared (NIR) excitation, including intense photoluminescence. Data obtained using both visible (514.5 nm) and NIR (779.1 nm) excitation are presented and the results are briefly discussed in the light of recent Fourier transform Raman studies using 1064.1 nm excitation.
The Raman spectrum of toluene vapour
Authors: Bican T. H. S. , Schrötter H. W. , Grošev V. Mohaček
Published: May 2005

The rovibrational Raman spectrum of toluene vapour at a pressure of 3 kPa was recorded photoelectrically at medium resolution. The sample was contained in a Brewster angle cell in the cavity of the argon ion ring laser of a CARS spectrometer, the scattered light being transferred to the Raman spectrometer by a fibre‐optic bundle. Nine fundamental bands, eight a1′ and one a2″, and some overtone bands were observed and assigned.
Specific molecular interactions of acridine drugs in complexes with topoisomerase II and DNA. SERS and resonance Raman study of m‐AMSA in comparison with o‐AMSA
Authors: Chourpa Igor , Manfait Michel
Published: May 2005

Molecular interactions of a potent DNA‐topoisomerase II (Topo II) inhibitor, m‐AMSA [4′‐(9‐acridinylamino)methanesulphon‐m‐anisidide] and of its less active isomer o‐AMSA in complexes with plasmid DNA, Topo II and Topo II‐mediated ternary cleavable complexes were studied by means of surface‐enhanced Raman scattering (SERS) spectroscopy. Models for the participation of these drugs in the complexes were proposed according to the analysis of the main vibrational modes of the acridine chromophores in the SERS and resonance Raman (RR) spectra of m‐AMSA in comparison with the structurally close derivatives o‐AMSA and 9‐aminoacridine (9AA). It was found that, under the conditions used, the adsorption on the silver colloid does not perturb the Raman spectra of acridine chromophores. The SERS data indicate the intercalation of the planar acridine moiety within DNA for 9AA and for both o‐AMSA and m‐AMSA, without pronounced differences for the meta and ortho isomers. The DNA intercalation is likely to involve a μ‐μ interaction between the acridine and DNA base pairs, but without contacts via the nitrogen of the acridine ring. This is because the spectral changes observed in the drug‐DNA complexes of m‐and o‐AMSA are different from those observed on acridine deprotonation. In fact, it is the NH group of the side‐chain of the drug that we propose to interact with the negatively charged phosphates or edges of DNA and stabilizes the arrangement of the external anilino ring in the minor groove of DNA. The DNA intercalation seems to be present for the acridine moiety of both isomers in the ternary cleavable complexes. However, in the latter the side‐chain of m‐AMSA, but not of o‐AMSA, has been found additionally to participate in specific (enzymatic activity‐dependent) interactions with Topo II. The SERS data indicate the ability of m‐AMSA to interact specifically with the enzyme alone. The specific m‐AMSA‐Topo II interactions on formation of the cleavable ternary complex and/or directly with the enzyme should play a key role in the Topo II inhibition and therefore in the anti‐tumour activity of the drug.
Non‐exponential dephasing of molecular vibrations in liquids, directly observed by ‘magic’ femtosecond CARS
Authors: Lindenberger F. , Rauscher C. , Purucker H.‐G. , Laubereau A.
Published: May 2005

Using ‘magic’ polarization geometries in time‐resolved coherent anti‐Stokes Raman spectroscopy, the isotropic (purely vibrational) scattering contribution was investigated. Non‐exponential dephasing was observed on the subpicosecond time‐scale, described in the Anderson‐Kubo formalism by the correlation time τc. Experimental data are reported for the neat liquids CH2BrCl and (CH3)2SO in the CH stretching region. Values of τc = 330 fs and 240 fs, respectively indicate, homogeneous line broadening for the dephasing processes. The time‐domain data are supported by a novel analysis of spontaneous Raman data.
UV resonance Raman spectroscopy of cis—‐amides
Authors: Jordan Trace , Spiro Thomas G.
Published: May 2005

UV resonance Raman (UVRR) spectroscopy with 210 nm excitation was used to study the cis‐amide bonds of caprolactam (CAP) and cis‐N‐methylacetamide (NMA) in aqueous solution. The UVRR spectrum of CAP is dominated by an intense stretching mode at 1492 cm−1, designated amide cII, which is assigned to a localized CN stretching vibration. The amide cI mode, described as a C=O stretch, can be located at 1621 cm−1 using Fourier transform IR spectroscopy. Photoisomerization of NMA with high laser power, followed by subtraction of the trans‐NMA spectrum, is used to generate the isolated UVRR spectrum of cis‐NMA and its (C)CD3, (N)CD3 and (C,N)CD3 methyl isotopomers. The spectrum of cis‐NMA is also dominated by an intense amide cII band at 1495 cm−1, and a weak band at 1623 + 3 cm−1 can be assigned to amide cI. The amide cII mode is strongly mixed with vibrations of the (N)CH3 group, as revealed by its 24 cm−1 downshift upon (N)CD3 substitution, but no isotopic sensitivity is observed for (C)CD3 substitution. Studies of CAP in various solvents show linear correlations between amide cI and cII wavenumbers and the solvent acceptor number, where amide cI downshifts and amide cII upshifts in hydrogen bonding solvents. However, the slope of the wavenumber dependence for the cis‐amide modes of CAP is smaller than for the corresponding trans‐amide modes of NMA and cannot be attributed to the differences in mode composition. This behavior is ascribed to different orientations of the ground‐state dipole for amides in trans and cis configurations. Finally, the selective enhancement of cis‐amide modes at 210 nm excitation was applied to monitor the increase in equilibrium population of cis‐NMA with increasing temperature. A Van't Hoff plot of the spectral data to calculate ΔH for cis‐trans isomerization yielded values of 1.9 + 0.2 kcal mol−1 from peak heights and 1.7 + 0.2 kcal mol−1 from peak areas (1 kcal = 4.180 kJ), which are in good agreement with previously published theoretical and experimental results.
New assignment of crystalline and ion‐irradiated graphite phonon spectra
Authors: Compagnini Giuseppe , Baratta Giuseppe A. , Cataliotti Rosario Sergio , Morresi Assuntina
Published: May 2005

A comparison was made between the Raman spectra of virgin and ion‐irradiated highly oriented pyrolytic graphite, relating them with their infrared spectra. Structural modifications, after ion beam irradiation at moderate ion fluences (0.2 eV per carbon atom, average deposited energy), were detected and a careful vibrational analysis was made in the light of the correlation between site and factor group symmetries of the graphite infinite crystal. This allows a new proposal for the assignment for the so‐called G and D lines of the Raman phonon spectra. Interaction effects, of the type projectile‐target, are envisaged to explain spectroscopic modifications of ion‐irradiated graphite.
Polarized Raman spectra and intensity analysis of Na4P2O7. 10H2O and PO stretches in (VO)2P2O7
Authors: Kanesaka Isao , Ozaki Kenichi , Matsuura Ikuya
Published: May 2005

The polarized Raman spectra of Na4P2O7 .10H2O and the infrared and Raman spectra in the polycrystalline state were recorded at room temperature. A normal coordinate analysis of Na4P2O7.10H2O and Raman and infrared intensity analyses in the P—O stretching region were carried out and the force field and the intensity parameters for the P2O ion obtained. These results were transferred and used to analyse the P—O stretches in (VO)2P2O7, whose infrared spectrum depends largely on the preparation method. It is concluded that α‐(VO)2P2O7 corresponds to the Gorbunova and Linde structure, while the γ‐form probably has disordered (VO) sites.
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

Changes 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

The 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

The 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

We 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

Transport 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

A 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

When 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

Formation 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

A 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

The 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

Mitochondrial 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

The 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

The 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

The 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

The 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

After 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

Modulation 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

An 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

Cells 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.
Differential phosphorylation of band 3 and glycophorin in intact and extracted erythrocyte membranes
Authors: Hosey M. Marlene , Tao Mariano
Published: May 2005

This report presents an analysis of the phosphorylation of human and rabbit erythrocyte membrane proteins which migrate in NaDodSO4‐polyacrylamide gels in the area of the Coomassie Blue‐stained proteins generally known as band 3. The phosphorylation of these proteins is of interest as band 3 has been implicated in transport processes. This study shows that there are at least three distinct phosphoproteins associated with the band 3 region of human erythrocyte membranes. These are band 2.9, the major band 3, and PAS‐1. The phosphorylation of these proteins is differentially catalyzed by solubilized membrane and cytoplasmic cyclic AMP‐dependent and ‐independent erythrocyte protein kinases. Band 2.9 is present and phosphorylated in unfractionated human and rabbit erythrocyte ghosts but not in NaI‐ or dimethylmaleic anhydride (DMMA)‐extracted membranes. These latter membrane preparations are enriched in band 3 and in sialoglycoproteins. The NaI‐extracted ghosts contain residual protein kinase activity which can catalyze the autophosphorylation of band 3 whereas the DMMA‐extracted ghosts are usually devoid of any kinase activity. However, both NaI‐ and DMMA‐extracted ghosts, as well as Triton X‐100 extracts of the DMMA‐extracted ghosts, can be phosphorylated by various erythrocyte protein kinases. The kinases which preferentially phosphorylate the major band 3 protein are inactive towards PAS‐1 while the kinases active towards PAS‐1 are less active towards band 3. The band 3 protein in the DMMA‐extracted ghosts can be cross‐linked with the Cu2+ ‐σ‐phenanthroline complex. The cross‐linking of band 3 does not affect its capacity to serve as a phosphoryl acceptor nor does phosphorylation affect the capacity of band 3 to form cross‐links. In addition to band 2.9, the major band 3 and PAS‐1, another minor protein component appears to be present in the band 3 region in human erythrocyte membranes. This protein is specifically phosphorylated by the cyclic AMP‐dependent protein kinases isolated from the cytoplasm of rabbit erythrocytes. The rabbit erythrocyte membranes lack PAS‐1 and the cyclic AMP‐dependent protein kinase substrate.
Crystallographic and chemical studies of the L‐arabinose‐binding protein from E. coli
Authors: Quiocho F. A. , Gilliland G. L. , Miller D. M. , Newcomer M. E.
Published: May 2005

The crystal structure of the L‐arabinose‐binding protein (ABP), an essential component of the high affinity L‐arabinose transport system in E. coli, has been determined at 3.5‐ and 2.8‐Å resolutions. The Fourier maps indicate that the molecule is ellipsoidal with overall dimensions of 70 × 35 × 35 Å (axial ratio ≃ 2:1) and consists of 2 distinct globular domains (designated “P” and “Q”). A tentative trace of the polypeptide backbone is presented. The 2 domains are arranged to create a deep and narrow cleft, the base of which is which is formed by 3 polypeptide chain segments linking the 2 domains. The arrangements of the secondary structure of the 2 domains are remarkably similar and can be related by a pseudo‐twofold axis. Each domain has a pleated sheet core with 2 helices on either side of the plane of the β sheet. This secondary structural arrangement is similar to that found in other proteins, specifically the dehydrogenases and kinases. The structural similarity is particularly intriguing in light of the recent finding in this laboratory that the dye 2′,4′,5′,7′‐tetraiodofluorescein, an adenine analogue which has been shown to bind to several dehydrogenases and kinases, binds to ABP with a dissociation constant of 30 μM.

Experiments performed with protein, modified with the chromophoric probe 2‐chloromercuri‐4‐nitrophenol (MNP), suggest that the binding site is near an essential cysteine residue: modification of the thiol with the mercurial dramatically decreases the ligand‐binding affinity of ABP, and conversely, the sugar protects the cysteine from reaction with MNP. The binding of L‐arabinose to MNP‐labeled protein perturbs the nitrophenol absorbance spectrum. The essential cysteine has been assigned to position 64 in the proposed chain tracing, which is consistent with the amino acid sequence. As an explanation for the failure of the difference Fourier analyses to locate the sugar‐binding site, it is postulated that the structure has been solved with the sugar bound. Electron density to which no amino acid residue can be assigned and which could be the sugar molecule is within van der Waals distance of the sulfur atom.
A role for anion transport in the regulation of release from chromaffin granules and exocytosis from cells
Authors: Pollard Harvey B. , Pazoles Christopher J. , Creutz Carl E. , Ramu Avner , Strott Charles A. , Ray Probhati , Brown Edward M. , Aurbach G. D. , Tack‐Goldman Karen M. , Shulman N. Raphael
Published: May 2005

Release of epinephrine from isolated adrenergic secretory veiscles from the adrenal medulla (chromaffin granules) was found to be inhibited by a number of anion transport blocking agents, including SITS, probenecid, pyridoxal phosphate, and Na‐isethionate. High concentrations of permeant anion, such as chloride, are required for granule release and the drugs were found to be competitive inhibitors with respect to chloride. The anion transport blockers were also found to suppress exocytosis of serotonin from human platelets and parathyroid hormone from dissociated bovine parathyroid cells. By contrast, they had no effect on ACTH‐activated corticosterone secretion from dissociated rate adrenocortical cells, a process which occurs by diffusion rather than exocytosis. The important anion in the medium for human platelets was hydroxyl ion, rather than chloride, and the most effective drug on platelets was suramin. Isethionate was inactive. In the case of PTH secretion, both chloride and hydroxyl ions were important anions and were both competitively inhibited by anion blocking drugs including Na‐isethionate. We conclude from these studies that the chemistry of exocytosis appears to be quite similar to the chemistry of release from isolated secretory vesicles. We suggest that when vesicles are fused to plasma membranes prior to exocytosis they are exposed to higher chloride and hydroxyl ion concentrations of the medium, and that inward anion flux into the vesicle promotes release, possibly by local osmotic lysis. Blockade of exocytosis by anion transport blocking drugs would occur by inhibition of inward anion flux into the fused vesicle, by analogy with previous results from studies on isolated chromaffin granules.
Surface antigens of the embryonic chick myoblast: Expression on freshly trypsinized cells
Authors: Friedlander Martin , Fischman Donald A.
Published: May 2005

Using an antiserum raised in rabbits against embryonic chick skeletal myoblasts (Anti‐M‐24), we have examined the trypsin and neuraminidase sensitivity and physiological expression of myogenic cell surface antigens. It was found that trypsin‐released muscle cells more effectively inhibited, on a cell to cell basis, the cytotoxicity of Anti‐M‐24 for 24‐h‐old myoblast monolayers than did identical cells that had received a 3–4 h suspension culture recovery period from trypsinization. There was no such difference in absorptive capacities observed for any other embryonic chick tissue tested (e.g. brain, retina, liver, heart, and red blood cells) when freshly trypsinized cells were compared to ones which were given a 3–4 h culture period. If freshly trypsinized muscle cells were treated with high concentrations (30,000 international units (IU)/0.1 ml packed cells) of trypsin or with neuraminidase (30,000 IU/ml packed cells), there was a selective loss of myoblast‐specific surface antigens. When single cells that had been in suspension culture for 3.5 h were reexposed to low concentrations (10,000 IU/0.1 ml packed cells) of trypsin, more antigenic sites were revealed on their surfaces as detected by an increased absorptive capacity in removing myoblast‐binding antibodies from Anti‐M‐24. This increase in antigenic expression was time‐dependent and inversely related to the length of culture time after trypsinization. Immunofluorescence studies revealed that tissue specific myoblast cell surface antigens are present on both muscle cells that were freshly dissociated and those that had been in suspension culture for 3–4 h. Furthermore, freshly trypsinized myoblasts possessed cell surface components that were highly antigenic; antiserum to such cells reacted extensively with both trypsinized and recovered muscle cells as detected by complement‐dependent 51Cr release cytotoxicity assays and immunofluorescence. We conclude that embryonic chick myoblasts prossess surface antigens that may be selectively removed by neuraminidase or high concentrations of trypsin. These antigens may be progressively masked, with increasing time of culture after protease‐dissociation, by molecules that are sensitive to low concentrations of trypsin. Such masking of tissue‐specific cell surface antigens could result in the display of molecular mosaics which may play a role in facilitating intercellular recognition and subsequent differentiation and histogenesis.
Energetics and molecular biology of active transport in bacterial membrane vesicles
Authors: Kaback H. R. , Ramos S. , Robertson D. E. , Stroobant P. , Tokuda H.
Published: May 2005

Bacterial membrane vesicles retain the same sidedness as the membrane in the intact cell and catalyze active transport of many solutes by a respiration‐dependent mechanism that does not involve the generation of utilization of ATP or other high‐energy phosphate compounds. In E. coli vesicles, most of these transport systems are coupled to an electrochemical gradient of protons (ΔμH +, interior negative and alkaline) generated primarily by the oxidation of D‐lactate or reduced phenazine methosulfate via a membrane‐bound respiratory chain. Oxygen or, under appropriate conditions, fumarate or nitrate can function as terminal electron acceptors, and the site at which ΔμH + is generated is located before cytochrome b1 in the respiratory chain.

Certain (N‐dansyl)aminoalkyl‐β‐D‐galactopyranosides (Dns‐gal) and N(2‐nitro‐4‐azidophenyl)aminoalkyl 1‐thio‐β‐D‐galactopyranosides (APG) are competitive inhibitors of lactose transport but are not transported themselves. Various fluorescence techniques, direct binding assays, and photoinactivation studies demonstrate that the great bulk of the lac carrier protein (ca. 95%) does not bind ligand in the absence of energy‐coupling. Upon generation of a ΔμH + (interior negative and alkaline), binding of Dns‐gal and APG‐dependent photoinactivation are observed. The data indicate that energy is coupled to the initial step in the transport process, and suggest that the lac carrier protein may be negatively charged.
Sialic acid: A specific role in hematopoietic spleen colony formation
Authors: Tonelli Quentin , Meints Russel H.
Published: May 2005

Vibrio cholerae neuraminidase (VCN) treatment of donor bone marrow cells results in a reduction in the number of hematopoietic colonies (CFUs) formed in the spleens of lethally irradiated mice. Treatment of marrow cells with sodium periodate under mild conditions, known to preferentially oxidze sialic acid, also reduced CFUs while subsequent potassium borohydride reduction restored CFUs to 80% of control levels. Innoculum viability as measured by in vitro incorporation of tritiated precursors into proteins, nucleic acids, and oligosaccharides was unaffected by VCN treatment. The ability of bone marrow cells in culture to respond to the hormone erythropoietin, as measured by the incorporation of 59Fe into cyclohexanone‐extractable heme, was also not affected by neuraminidase, making a cytotoxic effect of the VCN preparation unlikely. Incubation of VCN‐treated marrow with either β‐galactosidase or trypsin had no effect on the VCN‐induced reduction in CFUs. These results are consistent with the idea that membrane sialic acid plays a direct and specific role in the implantation and development of CFUs.
Dimensions and specificities of recognition sites on lectins and antibodies
Authors: Kabat Elvin A.
Published: May 2005

A comparison is made of the specific combining sites of a number of lectins and of antibodies with emphasis on those reacting with blood group A, B, and H determinants. The ranges of site sizes and specificities of both groups are similar both from immunochemical studies and from the limited x‐ray diffraction data available.