Applicability of polymer theories to the thermodynamics of proteins at the air/water interface: example of β-lactoglobulin

Knowledge of the equation of state of adsorbed or deposited layers of proteins at the air/water interface is of fundamental interest in the understanding of the surface activity of these molecules. Using scaling laws of current polymer theories, it has been shown that the equation of state of the interfacial layer in the semi-dilute regime should relate the surface pressure to the surface concentration through a power law. The exponent of this power law should reflect the quality of the solvent and the conformation of the adsorbed polypeptide chain. In the case of β-lactoglobulin layers, in the range of surface concentrations that should correspond to the semi-dilute regime, the relationship between surface pressure and surface concentration is expressed as a power law. The exponent of this power law is strongly influenced by the nature of the aqueous substrate and by the net charge of the protein molecule. The use of scaling laws gives a coherent view of the expansion of the polypeptide chain in the interfacial layer and of the relationship between surface concentration and surface pressure in the semi-dilute regime. This result favours a strong similarity between β-lactoglobulin and a polymer chain in the interfacial layer. It is concluded that current theories of polymer adsorption could be applied to interfacial protein layers.     

STRUCTRE AND PROPERTIES OF COMPOSITE Ni/HARD CARBON FILMS PREPARED BY PLASMA DEPOSITION

IntroductionHardcarbonfilmsprcparcdb}'vari0usplasmaprocesscsareofc0nsidcrablcinterestbccauscofthcirunusualmcchanical-opticalandelcctricalpropertiesll~3l.Rccently,ithasReceive(IJl111c5,l9`)5;,.`,1iis()tI1ie)\tioII,1'ceil'edJtl1)'l4,l995*'I11isprojectiss[1pportcdh}tl1cNatiol1a1Nat[lntlScicl1ccI`()ul1dati()l1ofCl1il1aal1dtl1eI,aboraton'ofSolidI,ubricati()l1,l.al1/l10ulnstitutcofCl1cn1icalPh\'sics,111cChincscAcadcl11\'ofScicnccs.benfoundthattheinc0rporati0nofmetaIintocarbonfilmscangrcatl}'…     

The importance of nonconventional structures in the binding of Ni<Superscript>+</Superscript> to ethynylsilanes and ethynylgermanes

The influence of the nature of the heteroatom on the Ni⁺ gas-phase binding energies of HCC–XH₃ (X is C, Si, or Ge) compounds has been investigated through the use of high-level density functional theory methods. The structures of the corresponding Ni⁺ complexes were optimized at the B3LYP/6-311G(d,p) level of theory. Final energies were obtained in single-point B3LYP/6-311+G(2df,2p) calculations. Nonconventional complexes, in which the metal cation interacts simultaneously with the CC system and with one of the X–H bonds of the substituent XH₃ group, play a significant role in the binding of Ni⁺ to HCC–XH₃ (X is Si or Ge) derivatives. Conversely, such nonconventional complexes are not local minima of the propyne–Ni⁺ potential-energy surface. This establishes a clear distinction between unsaturated carbon derivatives and the Si- and Ge-containing analogues as far as bonding to transition-metal monocations is concerned. Actually, the attachment of Ni⁺ to HCC–XH₃ (X is Si or Ge) compounds in the gas phase yields a mixture of conventional and nonconventional complexes. These agostic-type interactions can be viewed as a dative bond from the X–H bonding orbital toward the empty s orbital of the metal, and a back-donation from the valence electron pairs of the metal into the X–H antibonding orbital of the neutral species.Proceedings of the 11th International Congress of Quantum Chemistry satellite meeting in honor of Jean-Louis Rivail     

手性环丙烷类衍生物双水解转换的研究

具有四个新手性中心的螺环／环丙烷类化合物4在丙酮－12％HCl溶液中50℃下 发生双手性辅基－双水解转换反应，得到了手性环丙烷／双半缩醛类化合物，螺 [1-溴－4－羟基－5－氧杂－6－氧代双环[3.1.0]己烷－2，2′-(3′-亲核氧基－ 4′－羟基丁内酯）]（5），化学产率65％－79％，光学纯度ee≥98。通过元素分 析，[a]D^20,UV,IR,^1H NMR,^13C NMR,MS以及X射线四圆衍射测定，确认了它们的 化学结构、立体化学和绝对构型。该双半缩醛类化合物的合成方法学研究可为官能 团的转换，为某些复杂结构的手性化合物提供新的合成方法和途径。     

The decomposition of edta-gel precursors in the production of BSCCO superconductors

The decomposition of EDTA gel precursors for BSCCO superconductor manufacture has been studied using STA (TG/DTA) and dilatometry in conjunction with FTIR. The thermoanalytical data are discussed in relation to the sequence of phase formation necessary for the production of the 2223 BSCCO superconducting phase. The effects of substitution of Pb for Bi on the temperatures of formation of the superconducting phases is also discussed. STA has also been carried out under varying oxygen partial pressures to determine the effects of oxygen pressure on the formation and decomposition of the phases involved in the production of the 2223 compound.     

The interaction of double-charged metal ions with monolayers and bilayers of phospholipids

Electrophoretic mobilities of hexadecane/water emulsions containing dimyristoyl-phosphatidylcholine (DMPC) or egg yolk lecithin (EYL) monolayers at the interface and those of liposomes prepared from the same lipids were measured as functions of the concentrations of Ca²⁺, Mn²⁺, Cu²⁺, and Ni²⁺ cations in the aqueous phase. The surface potentials, surface charge densities (σ), and the Langmuir adsorption isotherms for various distances from the charged surface to the slip plane (d) were calculated on the basis of the Gouy-Chapman theory for 1∶2 electrolytes and the values of ζ-potentials. The binding constants (K) and parametersd were determined under the assumption that the maximum σ values correspond to one ion per phospholipid molecule at the interface. In the case of DMPC, the ion binding constants (L mol⁻¹) at 25°C are 230 and 87 for Ca²⁺, 31.5 and 21 for Mn²⁺, 11 and 6 for Cu²⁺, and 7.5 and 5.3 for Ni²⁺ in liposomes and emulsions, respectively. The affinities of Cu²⁺ and Ni²⁺ ions for EYL monolayers and bilayers are lower than those for DMPC mono- and bilayers. Thed parameters for all ions are smaller than the radii of the hydrated ions. In the case of Ca²⁺, Cu²⁺, and Ni²⁺, thed values for mono- and bilayers are different. The differences in K values between monolayers and bilayers as well as those between DMPC and EYL mono- and bilayers can be attributed to the differences in the local environment and orientation of the interfacial phosphate groups in these systems. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2490–2495, December, 1998.     

Highly conformationally constrained halogenated 6-spiroepoxypenicillins as probes for the bioactive side-chain conformation of benzylpenicillin

Summary The halogenated 6-spiroepoxypenicillins are a series of novel semisynthetic-lactam compounds with highly conformationally restricted side chains incorporating an epoxide. Their biological activity profiles depend crucially on the configuration at position C-3 of that epoxide. In derivatives with aromatic-containing side chains, e.g., anilide, the 3R-compounds possess notable Gram-positive antibacterial activity and potent-lactamase inhibitory properties. The comparable 3S-compounds are antibacterially inactive, but retain-lactamase inhibitory activity.Using the molecular simulation programs COSMIC and ASTRAL, we attempted to map a putative, lipophilic accessory binding site on the PBPs that must interact with the side-chain aromatic residue. Comparative computer-assisted modelling of the 3R, and 3S-anilides, along with benzylpenicillin, indicated that the available conformational space at room temperature for the side chains of the 3R and the 3S-anilides was mutually exclusive. The conformational space for the more flexible benzylpenicillin could accommodate the side chains ofboth the constrained penicillin derivatives. By a combination of van der Waals surface calculations and a pharmacophoric distance approach, closely coincident conformers of the 3R-anilide and benzylpenicillin were identified. These conformers must be related to the antibacterial, bioactive conformer for the classical-lactam antibiotics. From these proposed bioactive conformations, a model for the binding of benzylpenicillin to the PBPs relating the three-dimensional arrangement of a putative lipophilic S₂-subsite, specific for the side-chain aromatic moiety, and the 3-carboxylate functionality is presented.This work has been reported in preliminary form at the 4th Royal Society of Chemistry International Symposium on Recent Advances in the Chemistry of-lactam Antibiotics, Churchill College, Cambridge, U.K., 3–6 July 1988.     

Thermoanalytical studies of the processing of bulk and thin film BSCCO highT c superconductors by the Edita-Gel route

The decomposition of EDTA gel precursors for BSCCO superconductor manufacture has been studied using STA (TG/DTA) and dilatometry in conjunction with FTIR. Ther thermoanalytical data are discussed in relation to the sequence of phase formation necessary for the production of the 2223 BSCCO superconducting phase. Thin film preparation of Bi-based highT _c superconductors have been carried out on MgO (100). Grain orientation of oxide thin films has been investigated. Well orientated 2212 grains have been achieved, with the (001) planes parallel to the substrate. The EDTA-gel method has been modified by the addition of glycerol to achieve the appropriate viscosity for spin coating. STA has been used to study the decomposition of these modified gels for the formation of thin films.     

Single step synthesis of propionitrile over K/MgO from acetonitrile methylation with methanol

A series of potassium-doped MgO catalysts loaded with KOH up to 15 mol% was prepared and evaluated for a single step synthesis of propionitrile from acetonitrile methylation with methanol. As the amount of potassium dope increased, both the acetonitrile conversion and the selectivity toward propionitrile increased. Based on the activity data coupled with CO₂-TPD and NH₃-IR ones, it was concluded that potassium doping to MgO resulted in the enhancement of both basicity and bifunctionality — methylation and hydrogenation.     

Investigation of the phosphinyl analog of α-ketoglutaric acid

It was shown by³¹P and¹³C NMR spectroscopy that methyl(3-carboxy-3-oxopropyl)phosphinic acid (4-methylhydroxyphosphinyl-2-oxobutyric acid) (1) and the amide (2) of the latter exist in keto forms in non-aqueous solutions. In aqueous solutions an equilibrium between the keto,gem-diol, and enol forms has been observed. The proportions of the diol and enol forms increase as the acidity of the media increases. Silylation of acid 1 with hexamethyldisilazane gives the tris(trimethylsilyl) derivative of enol form (3) (Z- andE-isomers).Translated fromIzyestiya Akadetnii Nauk. Seriya Khimicheskaya, No. 1, pp. 125–128, January, 1994.