Synthesis and Biological Activity of Fatty Acid Derivatives of Quinine

Derivatives of quinine with fatty acids including polyunsaturated fatty acids were prepared. They showed moderate antimalarial activity as compared with quinine itself using Plasmodium falciparum. The activities were not dependent on whether the fatty acyl group was saturated or unsaturated. On the other hand, the derivatives showed significantly higher cytotoxicity against a mammary tumor cell line FM3A than quinine itself. Calculating from these data, an acetyl derivative of quinine with the shortest acyl group was found to give the highest selectivity.     

Secalonic acid D: natural contaminant of corn dust.

The mycotoxin secalonic acid D was detected for the first time as a natural contaminant of corn dust obtained from grain storage elevators. Secalonic acid D amounts ranged from 0.3 to 4.5 ppm (0.3 to 4.5 micrograms/g), as determined by reversed-phase high-performance liquid chromatography.     

The Oxyradical-Scavenging Activity of Azelaic Acid in Biological Systems

We have previously shown that azelaic acid, a C₉ dicarboxylic acid, as disodium salt (C₉2Na) is capable of inhibiting significantly the hydroxylation of aromatic compounds and the peroxidation of arachidonic acid due to reactive hydroxyl radicals (HO'). In this paper we have investigated the ability of C₉2Na to inhibit the oxyradical induced toxicity towards two tumoral cell lines (Raji and IRE 1) and normal human fibroblasts (HF). Oxyradicals were generated either by the addition of polyphenols to the medium, or by direct irradiation of phosphate buffered-saline in which cells were incubated from 15min prior to incubation in normal medium. The effects of C₉2Na were compared with those obtained by mannitol (MAN), superoxide dismutase (SOD) and catalase (CAT). C₉2Na, MAN, SOD and CAT significantly decreased the polyphenol toxicity towards cell lines cultured up to 24 h. After 48 h of incubation the above compounds lost the capability of protecting cells from polyphenol toxicity. This suggests that the toxic role of oxyradicals (O₂^-, H₂O₂, HO^.) persists for about 24h and, subsequently other toxic mechanisms must be involved, which are not affected by oxyradical scavengers. SOD and CAT did not show any protective effect on UV induced cytotoxicity, while both C₉2Na and MAN were capable of reducing significantly the UV damage towards cell lines, even after 48 h incubation. This can be explained by the fact that UV cytotoxicity depends mainly on the generation of HO', that can be “scavenged” by C₉2Na or MAN, but not by SOD or CAT. C₉2Na and MAN were not significantly degraded in the period during which they afford protection against HO^..     

生物法合成丙烯酸的研究进展

丙烯酸是一种重要的化工原料,被广泛应用于涂料、超吸附材料等领域。目前丙烯酸的获得主要通过丙烯氧化,但由于石油资源日渐枯竭以及生产过程造成的环境问题,利用生物质资源生产丙烯酸已成为研究热点。介绍了丙烯酸的性质及其在工业上的应用,并详细综述了生物法制备丙烯酸的研究进展。根据丙烯酸生产中是否应用传统的化工过程,将其分为半生物合成和全生物合成。半生物法主要包括乳酸化学法脱水以及丙烯腈、丙烯酰胺的生物转化;全生物法主要包括乳酸生物法脱水、3-羟基丙酸途径、糖直接发酵法以及DMSP(二甲基巯基丙酸内盐)途径。由于乳酸发酵的工艺成熟、原料易得,因此对乳酸脱水进行了重点介绍,其中生物法脱水符合可持续发展的要求,对其进行了详细介绍。同时还分析了各种方法的优缺点,探讨了利用生物质资源生产丙烯酸的研究趋势。     

D-焦谷氨酸的研制

研究了Ｄ－焦谷氨酸的制备,提纯精制以及分析化验等方面的有关问题。     

Practical Production of 6-O-Octanoyl-D-allose and Its Biological Activity on Plant Growth

The transesterification of D-allose (the C-3 epimer of D-glucose) with vinyl octanoate using Candida antarctica lipase in tetrahydrofuran proceeded with high regioselectivity to produce 6-O-octanoyl-D-allose with nearly complete conversion. The growth-inhibiting activity of 6-O-octanoyl-D-allose on lettuce seedlings was about 6-fold greater than that of D-allose.     

Regulation of Phospholipase D Activity and Phosphatidic Acid Production after Purinergic (P2Y6) Receptor Stimulation

Phosphatidic acid (PA) is a lipid second messenger located at the intersection of several lipid metabolism and cell signaling events including membrane trafficking, survival, and proliferation. Generation of signaling PA has long been primarily attributed to the activation of phospholipase D (PLD). PLD catalyzes the hydrolysis of phosphatidylcholine into PA. A variety of both receptor-tyrosine kinase and G-protein-coupled receptor stimulations have been shown to lead to PLD activation and PA generation. This study focuses on profiling the PA pool upon P2Y₆ receptor signaling manipulation to determine the major PA producing enzymes. Here we show that PLD, although highly active, is not responsible for the majority of stable PA being produced upon UDP stimulation of the P2Y₆ receptor and that PA levels are tightly regulated. By following PA flux in the cell we show that PLD is involved in an initial increase in PA upon receptor stimulation; however, when PLD is blocked, the cell compensates by increasing PA production from other sources. We further delineate the P2Y₆ signaling pathway showing that phospholipase Cβ3 (PLCβ3), PLCδ1, DGKζ and PLD are all downstream of receptor activation. We also show that DGKζ is a novel negative regulator of PLD activity in this system that occurs through an inhibitory mechanism with PKCα. These results further define the downstream events resulting in PA production in the P2Y₆ receptor signaling pathway.     

Milligram Production and Biological Activity Characterization of the Human Chemokine Receptor CCR3

Human chemokine receptor CCR3 (hCCR3) belongs to the G protein-coupled receptors (GPCRs) superfamily of membrane proteins and plays major roles in allergic diseases and angiogenesis. In order to study the structural and functional mechanism of hCCR3, it is essential to produce pure protein with biological functions on a milligram scale. Here we report the expression of hCCR3 gene in a tetracycline-inducible stable mammalian cell line. A cell clone with high hCCR3 expression was selected from 46 stably transfected cell clones and from this cell line pure hCCR3 on a milligram scale was obtained after two-step purification. Circular dichroism spectrum with a characteristic shape and magnitude for α-helix indicated proper folding of hCCR3 after purification. The biological activity of purified hCCR3 was verified by its high binding affinity with its endogenous ligands CCL11 and CCL24, with K _D in the range of 10⁻⁸ M to 10⁻⁶ M.     

Synthesis and Biological Activity of Nitrilic Derivatives of the Methyl Ester of Maleopimaric Acid

An effective method of a modification of the anhydride ring of the maleopimaric acid methyl ester by means of the cyanoethylation reaction was developed. A primary screening of a cytotoxic activity in vitro demonstrated an ability of the cyanoethyl derivative of the maleopimaric acid methyl ester to induce the death of the PC-3 cells of prostate cancer.     

Actinomycin Analogues Containing Pipecolic Acid: Relationship of Structure to Biological Activity

Streptomyces antibioticus synthesizes a mixture of actinomycins which differ at the "imino acid" site of the peptide chains. In the presence of exogenous pipecolic acid, several new actinomycins were synthesized and 70% of the proline in the antibiotic mixture was replaced by the analogue. Three new antibiotics (designated Pip 1alpha, Pip 1beta, and Pip 2) were isolated from culture filtrates, purified, and crystallized. The molar ratio of pipecolic acid to proline was: Pip 1alpha, 1:0; Pip 1beta, 1:1; Pip 2, 2:0. These compounds inhibited the growth and cell division of gram-positive, but not gram-negative, bacteria. The relative inhibitory activity against bacteria, Escherichia coli deoxyribonucleic acid (DNA)-dependent ribonucleic acid (RNA) polymerase in vitro, and RNA synthesis in Bacillus subtilis and mouse L-929 cells was: actinomycin IV = Pip 1beta > Pip 2 > Pip 1alpha. Protein synthesis in B. subtilis was less affected, and DNA synthesis was inhibited only at higher concentrations of antibiotic tested. In L cells, DNA formation was reduced less than RNA synthesis, whereas protein synthesis was not blocked under the experimental conditions employed. Kinetic studies with B. subtilis revealed that RNA synthesis was inhibited rapidly followed by an inhibition of protein synthesis. All four antibiotics markedly inhibited the replication of vaccinia virus and reovirus in tissue culture cells, but the production of poliovirus was resistant to the antibiotics. These actinomycins bind to DNA, resulting in an elevation of its T(m) and a decrease in the peak extinction of the actinomycins. The mode of action, as well as the structure-activity relationships among the actinomycins, are discussed relative to a previously proposed model of binding.     

Synthesis,Crystal Structure and Biological Activity of 2-Hydroxyethylammonium Salt of p-Aminobenzoic Acid

p-Aminobenzoic acid (pABA) plays important roles in a wide variety of metabolic processes. Herein we report the synthesis, theoretical calculations, crystallographic investigation, and in vitro determination of the biological activity and phytotoxicity of the pABA salt, 2-hydroxyethylammonium p-aminobenzoate (HEA-pABA). The ability of neutral and anionic forms of pABA to interact with TIR1 pocket was investigated by calculation of molecular electrostatic potential maps on the accessible surface area, docking experiments, Molecular Dynamics and Quantum Mechanics/Molecular Mechanics calculations. The docking study of the folate precursor pABA, its anionic form and natural auxin (indole-3-acetic acid, IAA) with the auxin receptor TIR1 revealed a similar binding mode in the active site. The phytotoxic evaluation of HEA-pABA, pABA and 2-hydroxyethylamine (HEA) was performed on the model plant Arabidopsis thaliana ecotype Col 0 at five different concentrations. HEA-pABA and pABA acted as potential auxin-like regulators of root development in Arabidopsis thaliana (0.1 and 0.2 mM) and displayed an agravitropic root response at high concentration (2 mM). This study suggests that HEA-pABA and pABA might be considered as potential new regulators of plant growth.     

Synthesis,Biological Activity and Decomposition Studies of Amino Acid Phosphomonoester Amidates of Acyclovir

Abstract

Highly stable and water soluble amino acid phosphomonoester amidates of acyclovir (ACV) were synthesized and shown to function predominantly as prodrugs of AC V and not acyclovir monophosphate (AC V-MP) with activities within two fold of the amino acid prodrug of ACV, valaciclovir (VACV). Metabolism studies revealed that incubation of cell-free extracts of Vero cells with the L-leucine phosphomonoester amidate of ACV (3c), resulted in a burst of ACV-MP production followed by the rapid generation of ACV.     

Effects of Physical and Chemical Treatments on the Biological Activity of Ricin D

Effects of physical and chemical treatments on the cytoagglutinating activity, toxicity and inhibitory activity of cell-free protein synthesis of ricin D or its constituent polypeptide chains were investigated. The results indicated that the isolated polypeptide chains were much less stable than intact ricin D in acidic pH, heating as well as chemicals, and the Ala chain was more unstable than the lie chain.

Chemical modifications of ricin D with specific reagents revealed that the tryptophan and tyrosine residues as well as the carboxyl groups participated in the phenomena of cyto- agglutination and toxic action of ricin D, whereas arginine residues were considered not to be directly involved. Trinitrophenylation of free amino groups did not result in a loss of cytoagglutinating activity, whereas caused a loss of toxicity, suggesting that free amino groups in the lie chain were involved in the toxic action of ricin D.     

Novel Vascular Endothelial Growth Factor D Variants with Increased Biological Activity

Members of the vascular endothelial growth factor (VEGF) family play a pivotal role in angiogenesis and lymphangiogenesis. They are potential therapeutics to induce blood vessel formation in myocardium and skeletal muscle, when normal blood flow is compromised. Most members of the VEGF/platelet derived growth factor protein superfamily exist as covalently bound antiparallel dimers. However, the mature form of VEGF-D (VEGF-D^ΔNΔC) is predominantly a non-covalent dimer even though the cysteine residues (Cys-44 and Cys-53) forming the intersubunit disulfide bridges in the other members of the VEGF family are also conserved in VEGF-D. Moreover, VEGF-D bears an additional cysteine residue (Cys-25) at the subunit interface. Guided by our model of VEGF-D^ΔNΔC, the cysteines at the subunit interface were mutated to study the effect of these residues on the structural and functional properties of VEGF-D^ΔNΔC. The conserved cysteines Cys-44 and Cys-53 were found to be essential for the function of VEGF-D^ΔNΔC. More importantly, the substitution of the Cys-25 at the dimer interface by various amino acids improved the activity of the recombinant VEGF-D^ΔNΔC and increased the dimer to monomer ratio. Specifically, substitutions to hydrophobic amino acids Ile, Leu, and Val, equivalent to those found in other VEGFs, most favorably affected the activity of the recombinant VEGF-D^ΔNΔC. The increased activity of these mutants was mainly due to stabilization of the protein. This study enables us to better understand the structural determinants controlling the biological activity of VEGF-D. The novel variants of VEGF-D^ΔNΔC described here are potential agents for therapeutic applications, where induction of vascular formation is required.Vascular endothelial growth factors (VEGFs)3 are considered as key growth factors inducing angiogenesis and lymphangiogenesis during embryogenesis as well as maintaining vasculature during adulthood. Their abnormal expression is found in pathological conditions such as cancer and retinopathies (1). Five mammalian VEGFs, VEGF-A, -B, -C, -D and placenta growth factor (PlGF), are known (2) as well as Orf virus-derived VEGF-E proteins (3) and multiple homologues from snake venoms (VEGF-Fs) (4). Several members of the VEGF family exist as different isoforms, either as a result of the alternative splicing of their mRNAs or due to proteolytic processing. These forms vary in their specificities and affinities to three main VEGF receptors, co-receptors such as neuropilins and heparan sulfate proteoglycans and other components of the extracellular matrix, translating into different biological effects (5).VEGFR-2 is an important receptor regulating vasculogenesis and angiogenesis. It is mainly expressed on endothelial cells, but expression is also found in several other cell types (6). Mammalian VEGFR-2 ligands include VEGF-A (7), VEGF-C (8), and VEGF-D (9). In addition to VEGFR-2, VEGF-C and VEGF-D are ligands for VEGFR-3, which mainly mediates lymphangiogenesis in adults but also participates in the formation of blood vessels during embryogenesis (2).Because of their importance in angiogenesis, VEGFs have been suggested as potential therapeutic agents in different pathological conditions to improve compromised blood flow. Studies aiming at inducing angiogenesis in vivo have been performed by introducing VEGFs to tissues either directly as recombinant proteins (10) or using gene therapy vectors (11). Findings from several laboratories have shown that VEGFs have strong angiogenic activity in vivo, and they could be used for the treatment of conditions like lower limb ischemia and ischemic coronary artery disease. The short in vivo half-life of these growth factors and the requirement for sustained angiogenic stimulus makes gene therapy a preferred option. Of the VEGFs, VEGF-A and the mature form of VEGF-D (VEGF-D^ΔNΔC, see below) are the strongest agents to induce vascular formation (12, 13).VEGFs share structural similarity with platelet-derived growth factors. Together they are classified as the VEGF/platelet-derived growth factor family, belonging to a larger family of cystine knot growth factors. The members of this family share a cystine knot motif, which is found in many extracellular proteins and is conserved among numerous species (14). Characteristic of the cystine knot proteins is that they contain a conserved structure of antiparallel β-sheets connected by three disulfide bonds. Typically cystine knot growth factors form dimers, which within the VEGF/platelet-derived growth factor family are often linked by intersubunit disulfide bonds. The crystal structures have been solved for VEGF-A (15), PlGF (16), VEGF-B (17), VEGF-E (18), and two snake venom VEGF-Fs, vammin and VR-1 (19).There are currently no published structures of VEGF-C or VEGF-D. They can be divided into their own subfamily based on sequence similarity and several characteristic features; 1) they are the only VEGFs that bind to VEGFR-3, 2) they are expressed as long precursor forms having poor receptor binding affinities, and 3) they require proteolytic processing at their N-terminal and C-terminal ends to become more active. In contrast to other members of the VEGF family, the mature, proteolytically processed ΔNΔC-forms of VEGF-C and VEGF-D exist predominantly as non-covalently bound dimers, even though they have the conserved cysteine residues that form the intersubunit disulfide bonds in other VEGFs (8, 20). However, both VEGF-C and VEGF-D also have an additional cysteine residue located at the dimer interface (8, 20). Mutation of this residue in VEGF-C only minimally altered the receptor binding affinity (21), but it stabilized the dimer structure (56).In the current study we investigated the importance of residues at the subunit interface for the function of VEGF-D^ΔNΔC. We built homology models of VEGF-D^ΔNΔC and used alanine scanning and site-specific mutagenesis as well as tested the biological activity of various mutated forms of VEGF-D^ΔNΔC. Our study revealed that the conserved cysteine residues (Cys-44 and Cys-53), which are known to form intersubunit disulfide bridges in other VEGFs, were essential for the activity of the recombinant VEGF-D^ΔNΔC. Furthermore, the monomer to dimer ratio of VEGF-D^ΔNΔC could be regulated by mutagenesis. In addition, it was found that replacement of the “extra” cysteine (Cys-25) by various amino acids, preferably Ile, Leu, or Val, actually enhanced the activity of VEGF-D^ΔNΔC. This was at least partially due to increased stability of the protein.     

烙铁头蛇毒L—氨基酸氧化酶的分离、纯化及其生物学活性

通过DEAESephadexA 5 0阴离子交换柱 ,SephadexG 75分子筛 ,ResourseQ阴离子交换柱三步层析从湖南产的烙铁头蛇毒中分离、纯化得到一个L 氨基酸氧化酶 (TM LAO) ,它由两个非共价的亚基组成 ,每个亚基的分子量为 5 5kD。与台湾产的烙铁头蛇毒L 氨基酸氧化酶分子量 ( 70kD)不同。TM LAO的N末端氨基酸序列是ADNKNPLEECFRETNYEEFLEIAR ,与报道的蝰科的L 氨基酸氧化酶的相似性比眼镜蛇科的要高。TM LAO能抑制大肠杆菌、金黄色葡萄球菌和痢疾杆菌的生长 ,杀死肿瘤细胞以及诱导血小板聚集。这些活性能被过氧化氢酶所抑制 ,说明TM LAO生理学功能主要是通过酶反应产生的过氧化氢 (H2 O2 )介导的     

Biological Activity of O-beta-d-Glucopyranosylzeatin

Concentrations of 10(-8) to 10(-5)m O-beta-d-glucopyranosylzeatin are less active than zeatin and zeatin riboside in the soybean (Glycine max L.) callus bioassay. At a concentration of 10(-4)m the glucoside was, however, more active or alternatively less toxic than similar concentrations of zeatin and zeatin riboside. Applied zeatin-O-glucoside is readily metabolized by soybean callus and both zeatin and zeatin riboside could be extracted from callus grown on basal medium containing the O-glucoside.