水/乙醇溶剂中阿奇霉素的热力学及多晶型研究

在278.2~308.2 K温度范围内,测定阿奇霉素在水/乙醇混合溶剂中的溶解度,根据固液平衡理论建立了该体系的溶解度修正模型。采用X线粉末衍射法和差示扫描量热法,对阿奇霉素在不同温度、不同体积比的水/乙醇混合溶剂中得到的晶体进行鉴别。同时利用溶解度数据估算了阿奇霉素在水/乙醇体系中的溶解热(-25.26~-16.11 k J/mol)、混合热(-9.94~-3.25 k J/mol)。通过溶液化学理论推导了阿奇霉素溶剂化平衡常数K与活度系数γ2的方程:γ2=1/(1+K),建立了溶剂化焓与温度、水/乙醇两者体积比(φ)之间的关系式,为ΔH=RTln(17.86exp(3.4φ)-1)。采用溶析结晶方法得到的6种阿奇霉素晶体,均属单斜晶系,但具有不同的晶胞参数且其密度和熔点也不同。同时发现温度越高,水/乙醇体积比越大,得到的晶体稳定性越差(晶体的熔点和密度降低)。在水/乙醇混合溶剂的溶析结晶体系中,产生阿齐霉素多晶型的现象与溶剂化作用的强弱有关。     

5’-三磷酸腺苷结晶热力学

5’-三磷酸腺苷（5’-ATP）是重要的生物活性物质,其结晶过程困难,是研究的热点。分别采用静态法和激光法测定了5’-ATP在不同温度的乙醇-水体系中的溶解度和介稳区宽度,并用溶解度模型——肌方程回归了溶解度数据,得到的溶解度关联方程为λ=19．034 3exp（-12．799w）,h：614．053exp（11．3106w）。研究表明．5’-ATP的溶解度随着温度的升高而升高,随着乙醇与水体积比r的升高而下降;其介稳区宽度随着温度的升高略有增大,随着乙醇与水体积比r的升高明显减小。这为5＇-三磷酸腺苷工业结晶装置及生产线的设计、工程放大和工业结晶生产操作提供了理论依据。     

聚谷氨酸批式生物合成的主要影响因素研究

采用Bacillus subtilisNX-2菌株,在5 L发酵罐批式操作过程中生物合成γ-聚谷氨酸,实验考察了搅拌转速(300~1 000 r/min)及底物质量浓度对生物合成γ-聚谷氨酸产率的影响。结果表明:转速为400 r/min时,γ-聚谷氨酸产率最高,可高达21.78 g/L。在转速400 r/min的条件下,考察了葡萄糖和谷氨酸浓度对聚谷氨酸生物合成的影响,根据葡萄糖初始质量浓度为40 g/L的实验数据建立了动力学方程。并在葡萄糖初始质量浓度为30,40,50,60g/L的范围内,验证所建动力学方程的稳定性和实用性。结果表明,在以上葡萄糖初始质量浓度范围内,所建模型对B.subtilisNX-2批式生物合成γ-聚谷氨酸产率的预测值与实验值能较好的吻合。     

生物组织超声散射系数与温度相关性的研究

在随机起伏介质超声散射理论基础上,根据生物非均匀介质中声波动方程,推导出散射系数与温度的关系,然后分别采用了回波直接截取、经验模态分层（EDM）两种方法进行实验验证分析.结果表明超声散射系数与温度有依次递增的对应关系,可以运用它从超声回波信号中有效地提取组织温度信息.经验模态分层法的数据处理结果一致性要好些,总体趋势更接近理论分析.     

甘氨酸和纳洛酮对减慢兔膈神经放电的高频振荡频率的递质的对抗作用

在25例清醒、肌肉麻痹、切断迷走神经的家兔,记录膈神经放电,以高频振荡(HFO)为指标,观察甘氨酸和纳洛酮对几种引起 HFO 频率减慢的递质的对抗作用。实验观察到,第四脑室内给予甘氨酸能对抗γ-氨基丁酸的 HFO 频率减慢作用,但甘氨酸不能对抗去甲肾上腺素、5-羟色胺、多巴胺或乙酰胆碱的 HFO 频率减慢作用。这提示在 HFO 形成机制中甘氨酸与γ-氨基丁酸存在相互作用。第四脑室内给予纳洛酮能对抗去甲肾上腺素、5-羟色胺、多巴胺、乙酰胆碱或γ-氨基丁酸的 HFO 频率减慢作用。因此,纳洛酮所起的对抗作用没有特异性。     

黄芩苷溶解性能的测定与表征

目的：充分了解黄芩苷的溶解性质,为黄芩苷类制剂的研究设计提供依据。方法：采用HPLC法测定黄芩苷在各溶媒中的溶解度,考察温度、pH值、表面活性剂等对其溶解度的影响,利用溶度参数理论探讨其溶解性能理论及表征其溶解性能。结果：黄芩苷在水中属几乎不溶的范畴;溶解度随着温度升高和pH值的增加而升高,溶解过程是吸热的,溶解度与温度的关系方程线性关系良好,可用于预测黄芩苷在设定温度下的溶解度;吐温80可提高黄芩苷的增溶度;黄芩苷在各溶媒中的溶解度大小与利用溶度参数表征黄芩苷溶解性能的结果吻合。结论：黄芩苷水溶性差、脂溶性均较差,可通过升温、调节pH值及加表面活性剂改变黄芩苷的溶解性质,可利用溶度参数理论对黄芩苷的溶解性能进行表征。     

5'-单磷酸腺苷在水和乙醇/水体系中的溶解度模型

以固-液平衡理论溶解度模型、适用于非理想体系的λh方程为理论基础,结合本实验结晶条件,采用静态法测定了5’-单磷酸核苷(5’-AMP)在纯水以及不同配比乙醇/水体系中的溶解度,建立了5’-AMP水和乙醇/水体系的结晶热力学模型。显示该体系属于缔合引起的非理想溶液,并计算水及乙醇/水体系的溶解热和结晶热,为5’-单磷酸腺苷的工业结晶生产提供了热力学数据。     

不同型别的基因工程干扰素抗病毒活性的比较

对大肠杆菌生产的不同型别的基因工程干扰素rIFN-α1(α1)、rIFN-αA(αA)、rIFN-β17ser(β17ser)和rIFN-γ(γ),以及自然人白细胞干扰素nIFN-αco,在不同细胞上对不同病毒的抗病毒活性做了比较研究。证明:①α1抗病毒作用的细胞谱较广,尤其在牛肾MDBK细胞和猪肾PK细胞上有很高的活性,分别为在人细胞上的29倍和7倍。β17ser和γ在异种细胞上活性极低,在鼠、猪和牛肾细胞上的活性为人细胞上的1～2％以下。②5种干扰素对麻疹、CoxB1、Sindbis、腺病毒7型和Ⅰ、Ⅱ型单纯疱疹病毒的抗病毒活性无明显差异。但不同病毒对干扰素的敏感性有明显差别,以Sindbis病毒为最敏感,7型腺病毒最不敏感。③5种干扰素对流行性出血热病毒均有明显的抗病毒作用,尤以人α1型和β干扰素作用最强,α1对出血热病毒的抗病毒活性是对滤泡性口膜炎病毒(VSV)的1/2.85,人β干扰素是对VSV的1/4.1。上述结果为人基因工程干扰素的临床应用提供了实验依据。     

用超临界流体技术萃取分离香茅油的研究

作者用超临界流体循环萃取装置对香茅油在超临界CO_2中的溶解度以及香茅油中主要成份香茅醛、香茅醇和香叶醇的分离特性进行研究。分别得出溶解度、分离特性与萃取压力、温度的关系及其相应的数学关联式。用这些关联式计算的结果符合工程需要,为单离香茅油工业化生产提供了理论基础。     

大刀锹甲Dorcus hopei的雄性三型现象及其在配偶竞争中的优势分析

【目的】大刀锹甲Dorcus hopei雄性的上颚和鞘翅长度存在显著的种内差异,本文旨在量化分析这些种内差异属于雄性三型,进一步通过实验研究它们在配偶竞争中的优势,为探索种内三型的共存机制提供参考。【方法】测量90只雄性成虫的上颚和鞘翅长度,通过高斯混合模型和基于AIC准则优选模型,识别出雄性三型;在此基础上,设计雄性的配偶竞争实验,借助红外相机记录不同表型组合的雄性接近雌性的时间长度和行为,用各型雄性占有雌性的时间长度来分析它们在配偶竞争中的相对优势。【结果】不连续的三分段模型对雄性成虫的上颚和鞘翅长度拟合最好（AIC最小）,这说明大刀锹甲的雄性可分为三个表型：α型具有发达的上颚和鞘翅,长度分别分14.70-18.84 cm和22.14-25.86 cm;γ型的明显短小,长度分别为4.88-8.99cm和15.42-19.40cm; β型的则居于α型和γ型之间,长度分别为11.67-15.99cm和19.24-23.77cm。配偶竞争实验表明,在二型雄性组合实验中,α型接近雌性的时间显著长于β型（P=0.007）和γ型（P=0.003）, β型接近雌性的时间显著长于γ型（P=0.01...     

Amino acid metabolism in euryhaline bivalves: regulation of glycine accumulation in ribbed mussel gills

Glycine levels in isolated ribbed mussel (Modiolus demissus) gill tissue increased slightly and decreased markedly when incubated at high and low salinities, respectively. Low levels of the enzymes involved in the biosynthesis of serine from triose phosphate intermediates, the serine hydroxymethyltransferase, and serine dehydrase were detected in gill tissue homogenates. Experiments using gill tissue incubated with (U-14C)-glycine and (U-14C)-serine indicated interconversion between serine and glycine and transfer of label to alanine, asparate, glutamate, CO2, organic acids, and protein. Glyoxylate was metabolized more slowly than glycine and was probably converted to glycine for catabolism. Studies using (1-14C)-glycine and (2-14C)-glycine with isolated gill tissue and mitochondria indicated that the mitochondrial glycine cleavage enzyme was the major route of glycine catabolism. Metabolic controls activating or inhibiting the glycine cleavage enzyme regulate tissue glycine accumulation and catabolism during hypersalinity or hyposalinity stress.     

Extent and stability of the alpha-helix in gamma-benzyl L-glutamate-glycine copolymers

Block and random copolymers of γ-benzyl L -glutamate and glycine were studied by optical rotatory dispersion methods in order to ascertain the extent and stability of the α-helix formed by these polymers in appropriate solvent mixtures. Results indicate that when in solution such polymers do contain sections of α-helix. However, it appears that glycine does not readily fit into the α-helix which is largely due to the γ-benzyl L -glutamate segments. Further, there are indications that the helical sections in the random copolymers are due to the nonrandomness of the polymerization.     

Release behavior of allyl sulfide from cyclodextrin inclusion complex of allyl sulfide under different storage conditions

The stability of allyl sulfide, an organosulfur compound present in garlic oil, in its α-, β-, and γ-cyclodextrin inclusion complexes was investigated under various storage conditions. The complexes of cyclodextrins and allyl sulfide were prepared by spray drying. The storage temperature, relative humidity, and initial moisture content of the inclusion complex had different effects on the release rate of allyl sulfide. Allyl sulfide in α-cyclodextrin complexes had a lower release rate than in β- and γ-cyclodextrin complexes at 100 °C and at 50 °C under 6, 40, 54, and 73% relative humidity. The initial moisture content affected only the release rate of allyl sulfide from α-cyclodextrin complexes. The release behavior of allyl sulfide can be correlated with the first-order release rate equation with a normal Gaussian distribution of free energy of activation of release rate constant. The results indicated α-cyclodextrin is a suitable material for controlled release of allyl sulfide.     

Identification of an ATP-driven, osmoregulated glycine betaine transport system in Listeria monocytogenes.

The ability of the gram-positive, food-borne pathogen Listeria monocytogenes to tolerate environments of elevated osmolarity and reduced temperature is due in part to the transport and accumulation of the osmolyte glycine betaine. Previously we showed that glycine betaine transport was the result of Na(+)-glycine betaine symport. In this report, we identify a second glycine betaine transporter from L. monocytogenes which is osmotically activated but does not require a high concentration of Na(+) for activity. By using a pool of Tn917-LTV3 mutants, a salt- and chill-sensitive mutant which was also found to be impaired in its ability to transport glycine betaine was isolated. DNA sequence analysis of the region flanking the site of transposon insertion revealed three open reading frames homologous to opuA from Bacillus subtilis and proU from Escherichia coli, both of which encode glycine betaine transport systems that belong to the superfamily of ATP-dependent transporters. The three open reading frames are closely spaced, suggesting that they are arranged in an operon. Moreover, a region upstream from the first reading frame was found to be homologous to the promoter regions of both opuA and proU. One unusual feature not shared with these other two systems is that the start codons for two of the open reading frames in L. monocytogenes appear to be TTG. That glycine betaine uptake is nearly eliminated in the mutant strain when it is assayed in the absence of Na(+) is an indication that only the ATP-dependent transporter and the Na(+)-glycine betaine symporter occur in L. monocytogenes.     

Identification of the site of glycation of γ-II-crystallin by (14C)-fructose

Cataract formation in diabetes may be via non-enzymic glycosylation (glycation) of lens proteins due to increased concentrations of sugars present in the lenses of diabetic patients. The objective of this project was to identify the site(s) of glycation of bovine γ-II-crystallin by [¹⁴C]fructose. γ-II-crystallin was isolated from soluble lens nucleus proteins by gel chromatography, followed by ion-exchange chromatography and was then glycated by incubation with [¹⁴C]fructose. Radioactively labelled γ-II-crystallin was cleaved with trypsin. Affinity chromatography of the tryptic peptides gave a single main peak containing the majority of the radioactivity. This indicated that fructose had reacted at a single site on the protein. Amino acid analysis of this peptide showed it to contain only lysine and a trace amount of glycine. By relating the results of the amino acid analysis to the amino acid sequence of γ-II-crystallin, it was concluded that the labelled peptide corresponded to the N-terminal dipeptide. The site of glycation of bovine γ-II-crystallin by fructose was thereby identified as the α-NH₂ group of the N-terminal glycine.     

Conformations of poly-L-valine in solution

In order to test theoretical predictions that poly-L -valine can exist in an α-helical conformation, water-soluble block copolymers of L -valine and D , L -lysine were prepared. By carrying out the synthesis on a resin support (with the use of N-carboxyanhydrides) contamination of the individual blocks by any unreacted monomer from the previous block was avoided. A single glycine residue was incorporated at the C-terminus of the chain for use in amino acid analyses. Using optical rotatory dispersion and circular dichroism criteria, about 50% of the short valine block of (D , L -lysine HCl)₁₈-(L -valine)₁₅-(D , L -lysine-HCl)1₆-glycine was found to be in the right-handed α-helical conformation in 98% aqueous methanol, in water, the polymer appears to be a dimer, with the valine block being involved in the formation of an intermolecular β-structure.     

Influence of age on NMDA receptor complex in rat brain studied by in vitro autoradiography

N-methyl-D-aspartate (NMDA) receptors are known to play an important role in learning and memory and to be involved in neuron cell death accompanying cerebral ischemia, seizures, and Alzheimer's disease. The NMDA receptor complex has been considered to consist of an L-glutamate recognition site, a strychnine-insensitive glycine modulatory site, and a voltage-dependent cation channel. In the present study, effects of age on an L-glutamate recognition site and a glycine site were examined in rat brain by quantitative in vitro autoradiography with [3H]-CPP and [3H]-glycine. Both [3H]-glycine and [3H]-CPP binding sites were most abundant in the hippocampus and cerebral cortex, and they showed a similar distribution pattern throughout the brain. [3H]-glycine binding sites were severely decreased in the telencephalic regions, including the hippocampus and cerebral cortex, in aged brain. Conversely, [3H]-CPP binding sites were well preserved in these brain areas. In the mid-brain regions and cerebellum, neither [3H]-glycine nor [3H]-CPP binding sites changed in the aged brain. Our results indicate that within the NMDA receptor complex, glycine receptors are primarily affected in the aging process.     

Purification and Properties of an Exocellular γ-Glutamyl Arylamidase from Bacillus sp. Strain No. 12

An exocellular γ-glutamyl arylamide-hydrolyzing enzyme was produced by a Bacillus sp. in L-glutamate-containing medium. This enzyme was a tetrameric simple protein composed of two heavy subunits (Mr 56,000) and two light subunits (Mr 46,000). It hydrolyzed γ-amido, acyl and aryl bonds in L- and D-glutamyl compounds, and the activity on L-glutamic acid γ-p-nitroanilide was inhibited by the addition of glutamate and γ-glutamyl compounds but not by α-glutamyl compounds. The activity was stimulated by various dipeptides but not by free amino acids, L-Alanine, glycine, L-serine and L-cysteine inhibited the enzyme competitively. Addition of hy-droxylamine had no effect on the activity.     

The aqueous solubility and thermal stability of α-lipoic acid are enhanced by cyclodextrin

We investigated the effects of various cyclodextrins (CDs) on the aqueous solubility and thermal stability of α-lipoic acid, a compound with low water solubility. α-CD, β-CD, and γ-CD had little effect on the aqueous solubility of α-lipoic acid. In contrast, 6-O-α-maltosyl-CDs increased it in a concentration-dependent manner, 6-O-α-maltosyl-β-CD enhancing solubility the most. The thermal stability of α-lipoic acid in the solid state was improved by the addition of G2-β-CD(?), a commercial product of 6-O-α-maltosyl-β-CD. The thermal stability of α-lipoic acid was also improved by the addition of β-CD. Analysis by differential scanning calorimetry showed that G2-β-CD(?), a mixture of maltosyl-β-CDs, and β-CD efficiently formed complexes with α-lipoic acid. These results suggest that the sizes and shapes of these β-CD compounds are compatible with complexation with α-lipoic acid. Moreover, both the formation of an aqueous complex with G2-β-CD(?) and an insoluble complex with β-CD increased the thermal stability of α-lipoic acid.     

STUDIES IN THE PHYSICAL CHEMISTRY OF AMINO ACIDS,PEPTIDES, AND RELATED SUBSTANCES : XI. THE SOLUBILITY OF CYSTINE IN THE PRESENCE OF IONS AND ANOTHER DIPOLAR ION

1. As an introduction to the relations that obtain in biochemical systems containing several components, some ionic, some dipolar ionic, the solubility of cystine has been investigated in the presence of glycine and neutral salts. 2. Both glycine and sodium chloride increase cystine solubility at all concentrations. The interaction between cystine and ions is, however, diminished with increase in glycine concentration, and the interaction between cystine and glycine with increase in ionic strength. 3. Sodium sulfate also increases the solubility of cystine, but at concentrations greater than one molal its solvent action is smaller than its salting-out effect, which is greater at all concentrations than that of sodium chloride, and greater the higher the glycine concentration. 4. These interactions are defined by an equation giving the solubility ratio of cystine in terms of salting-out constants, constants related to the electric moments of cystine, and to the ionic strength and dielectric constant of the solution. 5. The higher the concentration of glycine and therefore the dielectric constant of the solution, the smaller that part of the interaction between ions and dipolar ions which depends upon Coulomb forces and the greater appears the salting-out effect. 6. Conversely, the greater the ionic strength and the salting-out effect the smaller the interaction between dipolar ions in solution.