Amino acids and peptides. LV. Application of 2-adamantyl derivatives as protecting groups to the synthesis of peptide fragments related to Sulfolobus solifataricus ribonuclease. II.

Segment condensations were performed to construct peptide fragments related to Sulfolobus solifataricus Ribonuclease. At each condensation step, the new protecting groups were stable. The protected peptide fragments were treated with a low-high HF procedure to give the desired peptide fragments. These peptide fragments were also prepared by the solid-phase method, and the obtained peptides were compared with those obtained by the solution method. The peptide fragments obtained by the solution method were identical with those obtained by the solid-phase method on analytical HPLC, indicating that the new protecting groups could be easily removed by HF, and no racemization occurred during the synthesis of the protected peptides.     

Fluorimetric determinations of nucleic acids using iron, osmium and samarium complexes of 4,7-diphenyl-1,10-phenanthroline

New sensitive, reliable and reproducible fluorimetric methods for determining microgram amounts of nucleic acids based on their reactions with Fe(II), Os(III) or Sm(III) complexes of 4,7-diphenyl-1,10-phenanthroline are proposed. Two complementary single stranded synthetic DNA sequences based on calf thymus as well as their hybridized double stranded were used. Nucleic acids were found to react instantaneously at room temperature in Tris-Cl buffer pH 7, with the investigated complexes resulting in decreasing their fluorescence emission. Two fluorescence peaks around 388 and 567 nm were obtained for the three complexes using excitation lambda(max) of 280 nm and were used for this investigation. Linear calibration graphs in the range 1-6 microg/ml were obtained. Detection limits of 0.35-0.98 microg/ml were obtained. Using the calibration graphs for the synthetic dsDNA, relative standard deviations of 2.0-5.0% were obtained for analyzing DNA in the extraction products from calf thymus and human blood. Corresponding Recovery% of 80-114 were obtained. Student's t-values at 95% confidence level showed insignificant difference between the real and measured values. Results obtained by these methods were compared with the ethidium bromide method using the F-test and satisfactory results were obtained. The association constants and number of binding sites of synthetic ssDNA and dsDNA with the three complexes were estimated using Rosenthanl graphic method. The interaction mechanism was discussed and an intercalation mechanism was suggested for the binding reaction between nucleic acids and the three complexes.     

A method for bulk hydrogen analysis based on transmission and back scattering of fast neutrons

A method was proposed for bulk hydrogen analysis. It is based on simultaneous detection of transmitted fast neutrons and back scattered thermal neutrons from the investigated samples by ³He detectors. The fast neutron beams were obtained from ²⁵²Cf and Pu–Be neutron sources. The experimental set-up as well as samples preparation were described. Incident thermal neutrons beams obtained from either ²⁵²Cf or Pu–Be sources, were used to investigate the samples by neutron backscattering. The results obtained from transmission and backscattering of fast neutrons were compared and discussed. The advantage and capabilities of the proposed method were presented. The results obtained using fast neutron beams are more sensitive than those obtained using thermal neutron beams. Validation procedures were proposed to credit the results.     

Morphology control of polypropylene by crystallization under carbon dioxide

We investigated the crystalline morphology of isotactic polypropylene obtained by melt crystallization under carbon dioxide (CO₂) at various pressures. Spherulites consisting of regularly arranged fibrils without subsidiary lamellae were obtained by crystallization under CO₂ below 2 MPa, whereas large spherulites consisting of irregularly arranged fibrils with subsidiary lamellae were obtained under ambient pressure. Distorted domain crystals with uniform optical anisotropy consisting of α‐form were found to be obtained under CO₂ above 2 MPa, and needle crystals consisting of γ‐form were obtained above 12 MPa. Transmission electron micrographs showed that straight and thick lamellae are regularly arranged in both the distorted domain crystals and the needle crystals. The uniformly thick lamellae were confirmed by differential scanning calorimetry thermograms; that is, the melting temperature is higher and the melting peak is sharper than those obtained under ambient pressure. Such characteristic crystalline morphologies obtained under CO₂ may be attributed to local ordering in the melt state. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2738–2746, 2004     

Chemistry of Azobenzazole Systems. 3. Reactions of 2-Hydrazinobenzoxazole with Carbonyl Compounds

The reaction of 2-hydrazinobenzoxazole with various carbonyl compounds was studied. Only the corresponding azides were obtained with acylating agents such as acid anhydrides and acid chlorides and products with a fused triazole ring were not obtained. Only the corresponding hydrazones were obtained from furfural and 2-carboxy-3,4-dimethoxybenzaldehyde.     

牛血清白蛋白与保泰松和布洛芬相互作用的荧光光谱研究

应用荧光光谱法研究了保泰松和布洛芬与牛血清白蛋白分子间的相互作用,得到了分子间的结合常数和热力学参数．利用已有的计算方法,建立了相应的计算机程序,使计算结果更合理．通过与常见公式计算的结果进行比较,所建立的方法得到了比较满意的结果．同时考察了常见金属离子对药物与蛋白相互作用的影响．     

Thermodynamics of mixed electrolyte solutions. X. An isopiestic study of the quaternary system NaCl−KCl−MgCl2−H2O at 25°C

Activity coefficients in the aqueous quaternary system sodium chloridepotassium chloride-magnesium chloride were derived from isopiestic measurements at 25°C. The isopiestic data were treated by the various procedures of Scatchard, Friedman, and Reilly, Wood, and Robinson, and results obtained agreed fairly well with those obtained by pseudoternary transforms. Interaction parameters obtained indicated the preponderance of pairwise interactions. Excess Gibbs free energies of mixing were calculated.     

Effect of Microwave Activation on Polymerization Rate and Molecular Weight Development in Emulsion Polymerization of Methyl Methacrylate

Polymerization rate and molecular weight development experimental results for the emulsion polymerization of methyl methacrylate (MMA), in the presence of potassium persulphate (PPS) as initiator, and activated with a 50 W microwave source, are reported. The polymerization kinetics of the microwave activation experiment (MA) was compared against a traditional conductive heating (CH) polymerization reaction. The number average molecular weights, M_n, of the polymer samples obtained with microwave activation were significantly higher than those obtained from conductive heating. These high values of M_n were obtained from the beginning of the polymerization reaction. Polydispersity index (PDI) values in the range of 1.18 to 1.83 were obtained in the microwave irradiated samples. These values are lower than those produced by conventional emulsion polymerization of styrene and other vinyl monomers, and resemble the PDI values obtained in controlled‐radical polymerization processes. Polymer particles of submicron size (60 to 100 nm) were obtained.     

Characterization of kaolinite of the Baten El-Ghoul region/south Jordan by infrared spectroscopy

The infrared spectra (3700-500 cm-1) have been recorded for kaolinite obtained from the Baten El-Ghoul region/south Jordan. The spectra were recorded for raw and dried samples, using KBr disk and nujol methods. The vibrational assignments of the basic fundamental modes were proposed, which were supported by the spectra obtained from the two methods used. The results obtained were compared with other related studies.     

炔烃的钛氢化反应及产物的立体结构

通过色谱跟踪对炔烃的钛氢化反应进行了研究，反应前期可得到高选择性高产率的顺式烯烃，反应后期可得到高选择性高产率的反式烯烃，控制反应烯烃，控制反应时间，用酮类淬息方法分别得到了一系列新的专一立体构型的烯丙醇衍生物。     

Preparation of porous solids composed of layered niobate walls from colloidal mixtures of niobate nanosheets and polystyrene spheres

Macroporous solids with crystalline layered walls were fabricated from colloidal mixtures of size-controlled niobate nanosheets and polystyrene spheres. The macroporous solids, obtained after burning off the spheres, were characterized by scanning electron microscopy and X-ray diffraction. The obtained structures strongly depended on the lateral dimension L of the nanosheets used. When small nanosheets (L=100 nm) were used, partly ordered macroporous solids with interconnected pores were obtained, whereas sponge-like random macroporous structures were obtained with larger nanosheets (L=190 and 270 nm). Peapod-like hollow structures were obtained when we used small (L=190 nm) and very large (L=3 microm) nanosheets at the same time. The microstructure of the pore walls was controllable by changing the calcination conditions. The walls were composed of propylammonium/K(4)Nb(6)O(17) intercalation compound which has a layered structure with exchangeable cations in the interlayer space, stable up to 350 degrees C for 6 h on calcination. The walls were converted to crystalline K(8)Nb(18)O(49) after calcination at 500 degrees C for 6 h.     

Contrast ratio and switching of zigzag defect-free surface stabilized FLCD by photoinduced alignment

The contrast ratio and electro-optical switching behaviours of surface stabilized ferroelectric liquid crystal cells with alignment layers of a photodegradable polyimide prepared by polarized ultraviolet light irradiation have been investigated. The higher contrast ratio was obtained for a zigzag defect-free sample obtained by the photo-induced alignment method than by the rubbing method. The switching behaviours of the FLC, such as spontaneous polarization and response time, were measured. Higher spontaneous polarization and faster response times were obtained with cells prepared by the photoinduced alignment method. In addition, response times of the order of microseconds, which are fast enough to realize high quality moving images with video-frame rate, were obtained.     

Thermodynamics of mixed electrolyte solutions. XI. An isopiestic study of the quaternary system NaCl−KCl−CaCl2−H2O at 25°C

Osmotic and activity coefficients in the aqueous quaternary system sodium chloride-potassium chloride-calcium chloride were derived from isopiestic measurements at 25°C. The isopiestic data were treated by the various procedures of Scatchard, Friedman, and Reilly, Wood, and Robinson. The results obtained showed good agreement with those obtained by pseudo-ternary transforms. Interaction parameters obtained indicated the preponderance of pairwise interactions. Excess Gibbs free energies of mixing were calculated.     

Surface-enhanced raman scattering on silver-coated teflon sphere substrates

A simple experimental method for detecting organic species adsorbed on surfaces by surface-enhanced Raman scattering (SERS) is described. The rough silver surfaces were obtained by vapor deposition of Ag on teflon spheres of uniform size and shape on glass substrates. The spectra obtained from adsorbed phthalic acid, benzoic acid, and nitrobenzoic acid excited by the 514.5 nm substrates. The spectra obtained from adsorbed phthalic acid, benzoic acid, and nitrobenzoic acid these bands were not present and characteristic line spectra were obtained. The reproducibility of the method due to the well-defined roughness of the substrate constitutes a good tool by which theory can be tested.     

钴(Ⅱ)取代铜锌超氧化物岐化酶金属重组衍生物的电化学和光谱电化学研究

80年代Hill等［"在蛋白质的电化学研究中加人氧化还原促进剂以提高电极反应速率．但最近的研究表明,电极材料的选择、蛋白质的纯度和溶液的离子强度等都影响反应速率和吸附行为［'．我们曾选用悬汞电极在不加促进剂的情况下研究铜锌超氧化物歧化酶Cu。Zn。SOD的电化学性质,并获得较好的结果［'j．本文研究了钻（I）取代铜锌超氧化物歧化酶CO。CO。SOD的氧化还原行为,首先用热解石墨电极对CO。CO。SOD进行循环伏安研究,获得了电极反应为扩散控制的可逆的电化学过程;然后用光谱电化学技术进行论证,由2种方法得到了在CO。CO。…     

Formation of Anatase Nanocrystals-Precipitated Silica Coatings on Plastic Substrates by the Sol-Gel Process with Hot Water Treatment

Anatase nanocrystals-precipitated silica coatings were formed on plastic substrates such as poly(ethylene terephtalate) (PET), acrylic resin (AC) and polycarbonate (PC) from silica-titania gel coatings with and without addition of poly(ethylene glycol) (PEG) by hot water treatment. The maximum thickness of the coatings which can be formed without cracking or peeling-off was 100 to 200 nm for PET and PC substrates, whereas it was less than 50 nm for AC substrates. After a hot water treatment at 90°C for 120 min, the size of the anatase nanocrystals increased to be 30 and 50 nm for the coatings obtained with and without PEG, respectively. Anatase nanocrystals were formed throughout the whole of the coatings obtained with PEG and were formed only on the surface of the coatings obtained without PEG. Both coatings obtained with and without PEG were highly transparent. The plastic substrates with coatings obtained without PEG showed good weathering resistance owing to the protective effects of the residual silica under-layer. The coatings obtained with PEG showed higher photocatalytic activities than those obtained without PEG due to smaller size and higher dispersion of anatase nanocrystals in the coatings.     

Contrast ratio and switching of zigzag defect-free surface stabilized FLCD by photoinduced alignment

The contrast ratio and electro-optical switching behaviours of surface stabilized ferroelectric liquid crystal cells with alignment layers of a photodegradable polyimide prepared by polarized ultraviolet light irradiation have been investigated. The higher contrast ratio was obtained for a zigzag defect-free sample obtained by the photo-induced alignment method than by the rubbing method. The switching behaviours of the FLC, such as spontaneous polarization and response time, were measured. Higher spontaneous polarization and faster response times were obtained with cells prepared by the photoinduced alignment method. In addition, response times of the order of microseconds, which are fast enough to realize high quality moving images with video-frame rate, were obtained.     

Polycyclic Phosphorus-Containing Oxaboracyclanes

Abstract

The olygomers consisting of regularly repeating heterocyclic fragments were synthesized by the reaction of polycondensation of the ether of p-phenylenediboric acid and tetraoxymethyloldphosphioes obtained from the different diphosphines and aldehydes. The compounds with endocyclic phosphorus atom (I) were obtained in case of using the aliphatic aldehydes, and the compounds with exocyclic phosphoruscontaining group (II) were obtained when using the hydroxyaldehydes.     

Polymerization of DL-alanine NCA and L-alanine NCA

The polymerization of N-carboxy-DL -alanine anhydride and N-carboxy-L -alanine anhydride were carried out in various solvents such as acetonitrile, dimethyl sulfoxide (DMSO), and nitrobenzene. The x-ray diffraction diagram and the infrared spectra of the polymers of DL - and L -alanine were obtained. The polypeptides obtained in acetonitrile and in nitrobenzene were in the α conformation, and the conformation of polypeptide obtained in acetonitrile was not influenced by its molecular weight. The polypeptide obtained in DMSO was essentially in the β conformation. It was observed that the α and β forms of polyalanine were altered on treatment of the polymer with m-cresol, dichloroacetic acid, or formic acid.     

INAA of enamel and dentine samples of a group of children and adults: A comparative study

Instrumental neutron activation analysis (INAA) was applied to determine Ca, Cl, Mg, Mn, Na, Sr and Zn in dentine and enamel tissues from human permanent and deciduous teeth. Comparisons were made between the results obtained in these different dental tissues as well as those obtained in permanent and deciduous teeth. The findings obtained were also compared with the published data. The accuracy and the precision of the results were evaluated by analyzing certified reference material.