Peak recognition technique by a computer program copying the human judgement

Summary It is still difficult to determine peaks and peak boundaries properly, though peak recognition is very important for the precision of quantitative data. A new computer program overcomes these problems using a method which is adapted from human judgements. The algorithm was developed for HPLC but can also be used in other fields of analytical chemistry.     

Heptakis(6-deoxy-6-guanidino)-β-cyclodextrin: an artificial model for mitochondrial ADP/ATP carrier

Heptakis(6-deoxy-6-guanidino)-β-cyclodextrin, prepared by one-step reaction of heptakis(6-amino-6-deoxy)-β-cyclodextrin with 1H-pyrozolecarboxamidine, binds ADP/ATP very tightly.     

Chiral recognition in aqueous solutions. Preferential configurations of α-aminoacids bearing substituted alkyl chains at 25°C

Calorimetric measurements were carried out at 25°C on binary and ternary aqueous solutions containing L and D forms fo the following -aminoacids: tryptophan, cysteine, methionine, phenylalanine, histidine, threonine, and citrulline, which contain both hydrophilic and hydrophobic domains. Differences were found between the values of the homochiral and heterochiral pairwise enthalpic interaction coefficients for tryptophan, cysteine, and methionine. To the contrary, chiral recognition was not detected for phenylalanine, histidine, citrulline, and threonine. The data were interpreted in terms of a preferential configuration model. Chiral recognition is detected only when the interactions of the side chains in the homo- and heterochiral configurations are different. Chiral recognition disappears when a competition exists between zwitterion-zwitterion interactions and side chain-side chain interactions. In some cases, such as for citrulline, compensation effects can occur due to thermal contributions from different domains which mask chiral recognition.     

Alginate Properties and Heavy Metal Biosorption by Marine Algae

The physical properties of the alginate component in four different brown seaweeds (Sargassumfluitans, Ascophyllum nodosum, Fucus vesiculo-sus, andLaminaria japonica) were characterized using potentiometric titration,¹³C-nuclear magnetic resonance (NMR), chemical analysis, and viscosity measurements. The heavy metal binding capacities of the corresponding seaweeds were directly proportional to their respective total carboxyl group content, and related to the electronegativity of the elements investigated (Ca, Zn, Cd, Cu, and Pb). The uronic acid composition or sequence of the alginate component did not affect the metal uptake properties of the biosorbents studied here. However, the alginate leaching owing to its solubilization by Na ions was observed to decrease with increasing intrinsic viscosity of the extracted alginate, related to its molecular weight, and with increasing apparent acidic dissociation constant, related to the alginate density inside the biomass.     

Synthesis and Antiradical Activity of 5-Acetyl-2-alkylthio-4-aryl-6-methyl-1,4-dihydropyridine-3-carboxylic Acid Nitriles

The alkylation of 3-cyano-1,4-dihydropyridine-2(3H)-thiones or the condensation of an aromatic aldehyde, cyanothioacetamide, acetylacetone, and methyl iodide in the presence of piperidine has given a series of novel 5-acetyl-2-alkylthio-4-aryl-6-methyl-1,4-dihydropyridine-3-carboxylic acid nitriles. A compound was obtained from 3,5-di(tert-butyl)-4-hydroxybenzaldehyde in the molecule of which were combined the active part of the antioxidant ionol and a 1,4-dihydropyridine ring. It was found that, among the compounds synthesized, the highest antiradical activity occurred in a compound having two hydroxyl groups in the 4-phenyl substituent.     

DFT and CIS(D) theoretical study on the ground and excited states of pentanitrogen cation

Different isomers of N₅⁺ were modeled at DFT(PBE0)/aug-cc-pV(Q + d)Z, and their ground(transition) state characteristics were assessed through frequency calculations. Single-point energies were accomplished at PBE0/aug-cc-pV(5 + d)Z. Nonlinear optical susceptibilities (NLO) of isomers were accomplished using Firefly, while the linear optical invariant was examined using the finite-field method, Firefly, and modified dipole field tensor in the presence of two different screening factors. The excited states, singlets and triplets, of were modeled at the CIS and CIS(D) and then their optical parameters were estimated at TDFT(PBE0)/aug-cc-pV(Q + d)Z using Firefly. The singlet is found the most stable isomer, with the inversional rate constant larger than that of the Cs isomer and high energy barrier with the triplet counterpart. Isomers 2 , 3 , and 4 are found local minima, while 5 and 6 are saddle points: transition states between equivalent invertomers. Energy calculations of the singlet and triplet isomers were in excellent agreement with the literature. An excellent correlation is found between the average polarizability and the impulse factor. Substantial variations were found between the singlet and triplet excited states in terms of energy, geometry, and optical properties from one side and with from the other side. Reactivity indices showed that N1 and N5 are the optimum nucleophilic and electrophilic reactivity sites.     

新型手性Salen双核锌配合物的分子识别研究

合成了新型手性Salen配体（H3L）及新型手性Salen双核锌配合物（主体）.通过研究主体对咪唑类客体及氨基酸酯类客体的分子识别行为,测定了这些配位反应的缔合常数.主体对咪唑类客体分子识别的缔合常数顺序为:K(Im) >K(2-MeIm) >K(2-Et-4-MeIm).主体对氨基酸酯类客体分子识别的缔合常数顺序为:K(LeuOCH3) >K(ValOCH3) >K(AlaOCH3) >K(SerOCH3),配位数均为2.主体与D、 L型氨基酸酯分子识别反应在不同温度下的缔合常数结果表明,随着温度的升高,对映选择性下降.实验发现反应体系中存在焓熵补偿关系. CD光谱的研究结果也反映了主体对不同客体识别能力的差异.     

First radical cation salts of 2,5-bis(1,3-dithian-2-ylidene)-1,3,4,6-tetrathiapentalene (BDA-TTP) with copper(II) metal complex anions: β-(BDA-TTP)4Cu2Cl6 and (BDA-TTP)2CuCl4

New radical cation salts based on 2,5-bis(1,3-dithian-2-ylidene)-1,3,4,6-tetrathiapentalene (BDA-TTP) with copper(II) metal complex anions, β-(BDA-TTP)₄Cu₂Cl₆ and (BDA-TTP)₂CuCl₄, were synthesized and structurally characterized. Single crystals were prepared by electrochemical oxidation of BDA-TTP under galvanostatic conditions. X-ray diffraction study demonstrated that the salts have a layered structure, in which the conducting BDA-TTP layers alternate with the [Cu₂Cl₆]²⁻ or [CuCl₄]²⁻ anions. Both salts show the semiconductor-type temperature dependence of the conductivity. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 48–54, January, 2007.     

Shape-persistent cyclyne-type azamacrocycles: synthesis, unusual light-emitting characteristics, and specific recognition of the Sb(V) ion

Simple members of arene-azaarenecyclynes as a novel family of geometrically-controlled and shape-persistent azamacrocycles have been synthesized. Noteworthy is the specific recognition function for Sb(V). The synthesized azamacrocycles, in particular the Sb(V) complex, have unusually strong light-emitting property.