Regulation of calcium to tissue plasminogen activator secretion in mouse epidermal keratinocytes

The amounts of tissue plasminogen activator (tPA) of culture supernatants, cell surfaces as well as intracellular spaces of the mouse keratinocytes cultured in calcium-free medium or in the presence of low or high calcium concentration medium were tested using enzyme-linked immunosorbent assay (ELISA). The results indicated that cultured keratinocytes could secrete tPA into extracellular space and respond to the addition of high calcium concentration with a time-dependent increase of tPA secretion, and the peak value of tPA secretion appeared after 24 h of keratinocytes culture. Furthermore, comparing the amount of tPA in culture supernatants with that in cell surfaces, it was found that after culture for 24 h, the secreted tPA could bind to the surfaces of the keratinocytes through the lysine sites within its molecule, and this process was enhanced by high calcium concentration. On the basis of these data we assumed that in mouse keratinocytes, tPA firstly secretes into extracellular space and then binds to the keratinocytes surface, and calcium regulates tPA secretion and its following binding to the surface of keratinocytes, which may correlate with the differentiation of keratinocytes.     

Hydrogen generation of ammonia borane hydrolysis catalyzed by Fe22@Co58 core-shell structure

In this paper, the process of ammonia borane (AB) hydrolysis generate H₂ on the transition metal Fe@Co core-shell structure has been obtained. According to the different roles played by H₂O molecules and the number of H₂O molecules involved, there are three schemes of reaction paths. Route I does not involve the dissociation of H₂O molecules and all H atoms come from AB. Moreover, the H₂O molecule has no effect on the breaking of the BH bond or the NH bond. The reaction absorbs more heat during the formation of the second and third H₂ molecules. Route II includes the dissociation of H₂O molecules and the cleavage of BH or NH bonds, respectively, and the reaction shows a slight exotherm. Route III started from the break of the BN bond and obtained 3H₂ molecules through the participation of different numbers of H₂O molecules. After multiple comparative analyses, the optimal hydrolysis reaction path has been obtained, and the reaction process can proceed spontaneously at room temperature.     

Nucleophilic aromatic substitution of hydrogen through lithiated phosphine borane complexes and N-phosphorylphosphazenes

Organophosphorus compounds containing nitroaryl and cyanoaryl groups have been prepared in good yield through nucleophilic aromatic substitution of hydrogen using α-lithiated phosphazenes and phosphine borane complexes as nucleophiles. In all cases, nearly exclusive replacement of the hydrogen in the para position with respect to the activating group has been observed.     

Structural investigations on new iron-acyl derivatives of B(C6F5)3

Reactions between [Fe(η-C₅H₅)(MeCO)(CO)(L)], L = PPh₃ (1), PMe₃ (2), PPhMe₂ (3), PCy₃ (4), CO (5), and B(C₆F₅)₃ give new complexes [Fe(η-C₅H₅){MeCOB(C₆F₅)₃}(CO)(L)] L = PPh₃ (7), PMe₃ (8), PPhMe₂ (9), PCy₃ (10), CO (11), where B(C₆F₅)₃ coordinates selectively to the O-acyl groups. Hydrolysis of 7 gives [Fe(η-C₅H₅){HOB(C₆F₅)₃}(CO)(PPh₃)] (6). The X-ray structures of 6, 8 and 11 have been determined. Calculations, using density functional theory, demonstrate that the charge transfer to the acyl group on Lewis acid coordination is more significant in the σ than the π system. Both effects lead to a lengthening of the acyl C-O bond thus π populations cannot be inferred from the distance changes.     

乙醇胺合三（2－呋喃基）硼烷的分子和晶体结构

标题化合物乙醇胺合三（２－呋喃基）硼烷Ｃ＿（１４）Ｈ＿（１６）ＢＮＯ（Ｍｒ＝２７３．１０）的晶体属单斜晶系，空间群为Ｐ２＿１／ｃ，晶胞参数ａ＝１０．０５３（２），ｂ＝８．２１１（９），ｃ＝１６．５０９（２），β＝９５．０９°，Ｖ＝１３５７．３（７），Ｚ＝４，Ｄ＿ｃ＝１．３３ｇ／ｃｍ￣３，μ（ＭｏＫα）＝０．９０１ｃｍ￣（－１）。结构的偏离因子Ｒ＝０．０４５，Ｒ＿ｗ＝０．０４９。结构测定表明，呋喃环对硼原子的π电子反馈导致Ｂ─Ｃ键长极明显地缩短。由此可解释呋喃环与硼成键时所特有的共生倾向。     

手性噁唑硼烷催化的烷基(4-二烷基氨基)苯基酮的不对称硼烷还原

在手性硼杂噁唑烷催化下，用硼烷不对称还原了一系列烷基4-二烷基氨基苯基酮，结果表明由于存在催化剂和硼烷中的硼原子与氮原子的强络合作用，在该不对称还原中，该类酮比相应的烷基4-烷基、4-烷氧基、4-烷硫基酮表现出了较明显的取代基对对映选择性的影响。     

A new series of chiral catalysts for the enantioselective borane reduction of ketones

A new series of 1,3,2-oxazaborolidine catalysts substituted in position 4 by the (CH3)3C(CH2)n group (n=2, 3, 4, 5) were synthesized and applied to the borane reduction of prochi-ral ketones. The relationship between catalyst structure and enantioselectivity was discussed.     

A new ‘one-pot’ synthesis of hydrazides by reduction of hydrazones

A new, high-yielding methodology for reducing hydrazones to hydrazines is described, which allows the synthesis of different mono-, di- and trisubstituted hydrazines. Moreover, the reduction step can be followed by an in situ reaction with a carboxylic acid making possible a ‘one-pot’ synthesis of trisubstituted hydrazides. The method is relatively general and, in principle, suitable for industrial applications.     

Symbiodinolide, a novel polyol macrolide that activates N-type Ca channel, from the symbiotic marine dinoflagellate Symbiodinium sp.

A 62-membered novel polyol macrolide with a molecular weight of 2859 mu, symbiodinolide, was isolated from the symbiotic dinoflagellate Symbiodinium sp. Symbiodinolide exhibited a potent voltage-dependent N-type Ca²⁺ channel-opening activity at 7 nM and immediately ruptured the tissue surface of the acoel flatworm Amphiscolops sp. at 2.5 μM. The planar structure of symbiodinolide was elucidated by spectroscopic analysis and chemical degradations including hydrolysis and ethenolysis using the second-generation Grubbs' catalyst. Symbiodinolide was found to be a structural congener of zooxanthellatoxins. The relative stereochemistries of C26-C32, C44-C51, and C64-C66 parts, and the absolute stereochemistries of C69-73, C83-C103, and C3′-C18′ parts in symbiodinolide were established.