[reaction: see structure] The antioxidant activity of curcumin (1, 7-bis(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione) was determined by inhibition of controlled initiation of styrene oxidation. Synthetic nonphenolic curcuminoids exhibited no antioxidant activity; therefore, curcumin is a classical phenolic chain-breaking antioxidant, donating H atoms from the phenolic groups not the CH(2) group as has been suggested (Jovanovic et al. J. Am. Chem. Soc. 1999, 121, 9677). The antioxidant activities of o-methoxyphenols are decreased in hydrogen bond accepting media.
X-ray crystallographic studies were carried out for seven conglomerates, seventeen racemic compounds, and four enantiomerically pure salts of chiral primary amines with achiral monocarboxylic acids. The crystal structures of the conglomerate salts revealed that these crystals can be regarded as being an assembly of a characteristic columnar hydrogen-bond network in which the ammonium cations and the carboxylate anions are aligned around a 2-fold screw axis (21-column). On the other hand, the crystal structures of the racemic-compound salts could be broadly classified into two types. One type is a crystal consisting of 21-columns; the other type is a crystal consisting of a different type of columnar hydrogen-bond network in which the ammonium cations and the carboxylate anions are related by inversion centers (i-column). Our results suggest that both the formation and the assembly of 21-columns are essential in the formation of conglomerates from these salts, and that the difference in the packing of 21-columns between conglomerate salts and racemic-compound salts is governed by van der Waals interaction between the 21-columns.
Platelet glycoprotein (GP) Ib-IX-V is a multisubunit adhesion receptor that supports platelet attachment to thrombogenic surfaces at sites of vascular injury. The congenital absence of the receptor results in a bleeding disorder associated with "giant" platelets, a condition linking the expression of the complex to platelet morphogenesis. To understand better the expression of the GP Ib-IX-V complex, studies were undertaken to define the essential genetic elements supporting the expression of the ␣-subunit of the complex (GP Ib␣). GP Ib␣ promoter activity was evaluated by transfection of human erythroleukemia cells with reporter plasmids coding for the enzyme, luciferase. Studies were initiated with a fragment extending 2,738 nucleotides 5 to the transcription start site and lead to the identification of 253 nucleotides retaining full promoter activity in human erythroleukemia cells. In cells of nonhematopoietic lineage, human endothelial and HeLa cells, the GP Ib␣ promoter activity was no greater than background levels obtained with promoterless constructs. Gel shift assays and site-directed mutagenesis studies defined essential GATA and Ets binding motifs 93 and 150 nucleotides upstream of the transcription start site, a finding which further substantiates these elements as important determinants of megakaryocytic gene expression. The results define essential cis-acting elements responsible for the expression of GP Ib␣ and provide insights into molecular events coinciding with the release of normal platelets into the bloodstream.Basic information on the differentiation of megakaryocytes and the mechanisms responsible for the release of platelets into the bloodstream has significantly lagged behind basic studies of other cellular components of myeloid tissue. Major reasons for the lag have been the lack of suitable cell lines mimicking the unique properties of megakaryocytes in vitro. Certainly, the recently described c-Mpl ligand is essential for the differentiation of the pluripotent stem cell to a megakaryocyte (1-3), but the late events of the process, specifically those that result in the release of platelets from the mature megakaryocyte are still poorly understood. To this end, the expression of megakaryocytic or platelet-specific antigens is one unique aspect of megakaryocytopoiesis and platelet production that can be examined and the importance of such studies has been validated by the recent work identifying the transcription factor, NF-E2, as an essential genetic factor for platelet production (4).A role for the platelet membrane receptor, glycoprotein (GP) 1 Ib-IX-V, in platelet morphogenesis is suggested by the congenital absence of GP Ib-IX-V, a condition associated with the release of abnormal or "giant" platelets and referred to as the Bernard-Soulier syndrome (5, 6). The platelet GP Ib-IX-V complex is assembled from four distinct gene products, the ␣-and -subunits of GP Ib (GP Ib␣ and GP Ib), GP IX, and GP V (7-11). Considerable progress has been made defining the essential role of this recep...
The crystal structures of the diastereomeric salts of 1-arylethylamines with mandelic acid or p-methoxymandelic acid have been studied. This revealed that there was correlation between the efficiencies of the optical resolutions of the amines with the resolving reagents and the crystal structures of the salts. A characteristic hydrogen-bond layer, consisting of stable columnar structures and having a planar boundary surface, was found to be common to the less-soluble salt crystals; these crystals were considered to be stabilised from the viewpoint of both their hydrogen-bonding and van der Waals interactions. In contrast, in the corresponding more-soluble salts and in those diastereomeric salts which could not be separated by crystallisation, no such particularly stabilised crystal structure was formed; there only existed either columnar structures or planar boundary surfaces in these crystals. These results strongly suggest that for successful resolution it is necessary to realise a hydrogen-bond layer, consisting of stable columns and having planar boundary surfaces, in the crystals of one of the pair of diastereomeric salts. In order to achieve such a crystal structure, complementarity in molecular length between a target racemate and a resolving reagent must be considered the most important and fundamental factor.
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