Dilute solutions of nylon 12—II. Relationship between intrinsic viscosity and molecular weight

Samples of poly(12-dodecanelactam) (polylaurolactam, nylon 12) with $\text{M}$_n 1 × 10³?33 × 10³ were prepared. Polymerizations initiated with water or with lauric acid proceeded under conditions for minimum changes in end-group concentration. Values of $\text{M}$_n were calculated from the end-group content and $\text{M}$_n from light scattering in the mixture m-cresol/60 vol% of 2.2,3,3-tetrafluoropropanol. From measurements of intrinsic viscosity in m-cresol, the relationship [n] ? $\text{M}$_n was established in the given range of $\text{M}$_n. The relationship [n] ? $\text{M}$_w for $\text{M}$_w from 3.3 × 10³ to 125 × 10³ has been established.     

A study of 1,2,3,4-tetrahydro-4-azafluorene-3,9-diones

Intramolecular cyclization of the diamides and N,N-dimethylamides of -[indan-1,3-dion-2-yl]benzylmalonic acids (I) has given 1-aryl-2-carbamoyl-1,2,3,4-tetrahydro-4-azafluorene-3, 9-diones and 1-aryl-4-methyl-2-methylcarbamoyl-1,2,3,4-tetrahydro-4-azafluorene-3,9-diones (II). The structure of compounds II was shown by chemical methods: bromination, xanthylation, and hydrolysis in alkaline and acid media, and also by a study of IR and UV spectra.     

A microcalorimetric study of the action of mercuric chloride on the metabolism of mitochondria isolated from Cyprinus carpio liver tissue

After the occurrence of 'Minamata disease' in 1950, mercury aroused much more attention, and lots of studies concerned have been made. The purpose of the present paper is to study the effect of mercuric chloride on the mitochondria suspension isolated from the liver tissue of Cyprinus carpio from the direct viewpoint of energy by using the microcalorimetric method. The metabolic thermogenic curves of the mitochondria suspension at 25°C were obtained, and the mitochondria metabolic thermokinetic equations were established, from which we obtained the thermodynamic and thermokinetic parameters: thermogenic rate constant (k), heat output (Q), average heat power (P_av), etc. Experimental results indicated that low concentration of mercuric chloride (5 nmol Hg²⁺/(mg protein)) stimulates the thermogenesis of mitochondria, suggesting a strong effect of uncoupling action, while high concentration of mercuric chloride (20 nmol Hg²⁺/(mg protein)) inhibits the metabolism of mitochondria completely, suggesting a fatal effect on the phosphorylation system. The effect of Hg²⁺ on mitochondria is concentration-depended, from which the probable reaction mechanism of Hg²⁺ to the mitochondria was proposed. So the microcalorimetric method can be used in the toxicology research.     

Quantum scattering calculation of the O(1D)+HBr reaction

Three-dimensional time-dependent quantum wave packet calculation for the O((1)D)+HBr reaction has been carried out using an accurate ab initio global potential energy surface [K. A. Peterson, J. Chem. Phys. 113, 4598 (2000)]. The calculations show that the initial state-selected reaction probabilities are dominated by resonance structures, and the lifetime of the resonance is generally in the subpicosecond time scale. The energy dependence of the reaction cross section is computed, which manifests still resonance structures, and is a decreasing function of the translational energy. The thermal rate constants are also computed, which are nearly independent on the temperature. The calculation results are discussed and compared to similar reaction with deep well.     

Ionic strength dependence of formation constants, protonation, and complexation of aspartic acid with dioxovanadium (V)

The stability constants of complexes of dioxovanadium (V) ion and L-asparrtic acid were determined potentiometrically at various ionic strengths of I = 0.1, 0.3, 0.5, and 0.7 mol. dm⁻³ at 25°C. A sodium chloride solution was used to maintain the ionic strength. The parameters based on these formation constants were calculated and the dependence of protonation and the stability constants on ionic strength are described by a Debye-Huckel type equation.     

Electrospray ionization mass spectrometry of ionic liquids and determination of their solubility in water

Electrospray ionization mass spectrometry is used to detect both the cations (C⁺) and the anions (A^–) of ionic liquids (CA). In this study, the ionic liquids are diluted with aqueous methanol before injection. In addition to the main peaks of the parent ions, fragmentation products are observed upon increasing the cone voltage, whereas aggregates of the parent ion with one or more ionic liquid molecules (e.g., C(CA)_n⁺, A(CA)_n^–) are observed upon decreasing the cone voltage. The ions of several ionic liquids in a mixture are also detected and the ratios of their concentrations estimated. A method is developed to determine quantitatively the concentration of an ionic liquid in solution by using the cation and anion of another ionic liquid as internal standards. By using this method, the solubilities in water at room temperature (22±1 °C) of three typical hydrophobic ionic liquids have been determined: 0.70±0.08 g L^–1 for methyltributylammonium bis(trifluoromethylsulfonyl)imide (MeBu₃NNTf₂), 6.0±0.5 g L^–1 for butylmethylpyrrolidinium bis(trifluoromethylsulfonyl)imide (BuMePyrNTf₂), and 18.6±0.7 g L^–1 for 1-butyl-3-methylimidazolium hexafluorophosphate (BMIPF₆).     

ICP-AES detection of silicon carbide impurities volatilized in a graphite furnace with the use of carbon tetrachloride vapour

The analytical capability of high-temperature halogenation with carbon tetrachloride vapour in a graphite furnace was investigated for silicon carbide powder with known chemical composition and particle size. Intensity vs heating time curves were determined for analytical lines of Al, B, Ba, Ca, Cr, Cu, Fe, Mg, Mn, Ti, V and Si constituents, volatilized with and without the presence of CCl₄ vapour in the furnace atmosphere. Igniting 10 mg SiC at 2100 °C for 60 s in chlorinating atmosphere, the evaporated fraction of most of the constituents was higher than 90% (for Al about 50%). The line intensity vs sample mass (4–26 mg) relationships were linear for all impurities studied, while the intensity of silicon line showed a relatively small change with the sample mass. BEC (background equivalent concentration) values for this solid sampling technique (10 mg loaded sample) were 2–20 fold lower than those calculated for the conventional solution sample introduction method.     

二(1,3-二硫杂环戊烯-2-硫酮-4,5-二巯基)镉-季铵类配合物的合成与表征

二（１，３－二硫杂环戊烯－２－硫酮－４，５－二巯基）镉－季铵类配合物的合成与表征李洪启宋燕西＊周宏英王爱勤姚钟麒俞贤达（中国科学院兰州化学物理研究所，兰州７３００００；＊兰州大学化学系，兰州７３００００）关键词二（１，３－二硫杂环戊烯－２－硫酮－４，...     

Influence of the glycoproteins of the cotton plant on the biosynthesis of proteins and nucleic acids

An inhibitory action of ELPs and LLPs on the inclusion of³H-thymine and³⁵S-methionine in the cells of a suspension culture and isolated nuclei of cottonplant seedlings has been found. The influence of the ELPs on the proliferative activity of cottonplant cells and of the ELPs and LLPs at the level of protein biosynthesis in isolated nuclei bears a dose-dependent nature, in contrast to the galactose-specific fraction LLP-1.A. S. Sadykov Institute of Bioorganic Chemistry, Academy of Sciences of the Republic of Uzbekistan, Tashkent, fax (3712) 62 70 71. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 865–870, November–December, 1997.     

Synthetic oligopeptides as isoelectric point markers for capillary isoelectric focusing with ultraviolet absorption detection

Sixteen peptides (trimers to hexamers) were designed for use as a set of pI markers for capillary isoelectric focusing (CIEF). Each peptide contains one tryptophan residue for detection by UV absorption and other amino acid residues having ionic side chains, which are responsible for focusing to its pI. The pIs of these peptides were determined by slab-gel IEF using commercial carrier ampholytes. The focused peptides in the gel were detected by absorption measurement at 280 nm using a scanning densitometer and the pH gradient was determined by measuring the pH of the gel using an oxidized metal membrane electrode. The pI values of the peptides ranged from 3.38 to 10.17. The obtained values agreed well with the predicted ones, which were calculated based on amino acid compositions, with root mean square differences of 0.15 pH unit. The peptides were detected at 280 nm as very sharp peaks when separated by CIEF. The pI values of some standard proteins were redetermined by CIEF by using this set of peptide pI markers and the values agreed closely with those reported previously. The sharp focusing, stability, high purity and high solubility of these synthetic pI markers should facilitate the profiling of a pH gradient in a capillary and the determination of the pI values of proteins.