四种新鲜蔬果中酪氨酸酶的提取及其动力学研究

目的:从新鲜蔬果中提取酪氨酸酶,对得到的酪氨酸酶提取液分别进行动力学研究,计算酶的活性。方法:从苹果、马铃薯、紫茄子、雪梨中提取酪氨酸酶,以邻苯二酚溶液为底物,测定不同浓度的酪氨酸酶活性,建立动力学方程。结果:在最大吸收波长λmax为409 nm处,不同蔬果中,苹果、马铃薯、紫茄子及雪梨的酪氨酸酶活性分别为194.62 U/g、135.39 U/g、156.81 U/g及239.12 U/g。结论:以邻苯二酚为底物,以pH=6.8磷酸盐缓冲溶液测定酪氨酸酶的活性,效果好。     

奥扎格雷对蘑菇酪氨酸酶的抑制机理研究

以L-DOPA为底物,抗血小板凝聚药奥扎格雷对酪氨酸酶具有很强抑制性,导致酶活力下降50%的奥扎格雷浓度(IC50)为3.45 mmol/L。奥扎格雷对酪氨酸酶抑制作用表现为可逆的竞争性和反竞争性混合型的抑制。按邹承鲁[1]所介绍的酶失活过程中的底物反应动力学方法测定奥扎格雷对酪氨酸酶的抑制作用动力学,1.0 mmol/L的奥扎格雷对酪氨酸酶和酪氨酸酶-底物复合物的抑制作用动力学常数分别为87.28和66.07μmol/L。     

中华猕猴桃水提液清除羟自由基以及抑制酪氨酸酶活性的研究

以Fenton反应产生羟自由基,测定中华猕猴桃水提液清除羟自由基的能力。以L-酪氨酸和L-多巴为底物,测定中华猕猴桃水提液对酪氨酸酶单酚酶和二酚酶活力的影响以及抑制动力学。实验结果表明:中华猕猴桃水提液对羟自由基有较好的清除作用,当水提液质量浓度为1.0 g/L时,羟自由基清除率达到了95.57%。中华猕猴桃水提液对酪氨酸酶单酚酶和二酚酶的活性均有较好的抑制作用,其半数抑制浓度(IC_(50))分别为0.28和0.35 g/L。动力学研究表明,中华猕猴桃水提液对酪氨酸酶二酚酶的抑制作用属于可逆过程,其抑制作用表现为混合型抑制。     

三种美白剂对酪氨酸酶活性的抑制

酪氨酸酶为黑色素生成的关键酶 ,抑制其活力即可抑制黑色素的生成。用L -酪氨酸酶作底物 ,体外测定了三种常用美白剂 (对苯二酚、熊果苷、曲酸 )对酪氨酸酶活性的影响。发现这些美白剂均能不同程度地抑制酪氨酸酶活性 ,并初步探讨了其增白作用的机制。     

催化合成美白剂4-(1-苯乙基)-1,3-苯二酚及其性能研究

采用浸渍法制备了二氧化硅负载磷钨酸催化剂,使用IR、XRD和SEM对其进行了表征,并用该催化剂催化间苯二酚与苯乙烯反应合成了美白剂4-(1-苯乙基)-1,3-苯二酚,经二甲苯重结晶后使用MS和~1H NMR确定了产物的结构;应用酪氨酸酶活性抑制实验、Fe~(3+)还原力和自由基抑制实验评价了4-(1-苯乙基)-1,3-苯二酚的美白和抗氧化活性,并与β-熊果苷进行了比较。结果表明,以L-酪氨酸为底物时,4-(1-苯乙基)-1,3-苯二酚对酪氨酸酶的半抑制浓度IC_(50)=0.010 5 g/L,明显低于β-熊果苷(IC_(50)=0.64 g/L),4-(1-苯乙基)-1,3-苯二酚的美白效果远强于β-熊果苷;4-(1-苯乙基)-1,3-苯二酚对Fe~(3+)还原力的半效应浓度EC50=0.033 g/L,去除羟基自由基的EC_(50)=0.06 g/L,去除超氧自由基的EC50=0.32 g/L,与β-熊果苷的抗氧化能力相比,其对Fe~(3+)还原力和去除超氧自由基的能力强于β-熊果苷。     

薰衣草花提取物对酪氨酸酶的抑制作用研究

以薰衣草花为原料,经体积分数为70%乙醇提取,将提取物浓缩成浸膏后用水分散,再依次用石油醚、氯仿、乙酸乙酯和正丁醇依次萃取。以L-DOPA为底物测定石油醚、氯仿、乙酸乙酯和正丁醇萃取部分及萃取后水相部分对酪氨酸酶的抑制作用。实验结果表明,薰衣草花水相萃取物对酪氨酸酶有较强的抑制作用,IC50为0.96 g/L,动力学研究表明,薰衣草花水相萃取物对酪氨酸酶的抑制作用是可逆的,其抑制类型为线性混合型抑制,对游离酶和酶-底物络合物的抑制常数分别为3.00和12.00 g/L。     

茶皂素的纯化及抑制酪氨酸酶活性的研究

研究了茶皂素的纯化及纯化产物体外对马铃薯酪氨酸酶催化L-DOPA合成多巴醌的抑制作用及其机理。结果表明质量浓度为100 g/L时,市售茶皂素、经大孔树脂纯化的茶皂素TS及2种层析分离得到的茶皂素TS1和TS2对酪氨酸酶的抑制率分别为51.29%,90.06%,94.13%和82.47%;TS和TS1对酪氨酸酶IC50分别为48和40 g/L,抑制作用表现为可逆竞争性抑制,对酪氨酸酶的抑制常数分别为137和101 g/L。     

白芷与茯苓美白保湿面膜的制备及性能研究

在传统面膜工艺的基础上,添加白芷和白茯苓有效提取成分,经过对面膜液保湿效果的探讨,筛选出最佳的面膜液配方,得到一款新型白芷和白茯苓中药美白保湿面膜,美白效果显著、保湿性能极佳。通过体外抗氧化测试(清除DPPH·自由基)、酪氨酸酶的抑制研究和毒理学研究,发现该面膜的保湿率达到98.2%,DPPH·的清除率为75%,对酪氨酸酶的抑制活性IC_(50)值为0.87 g/L,安全性极高,经对大鼠的皮肤和眼睛测试,结果均无明显刺激性。     

海参水煮液皂苷的美白抗衰老功效研究

为开发海参水煮液皂苷在化妆品领域的应用,对海参水煮液进行了醇沉、大孔树脂吸附和乙醇梯度洗脱,获得三种海参皂苷组分S1、S2、S3,采用红外光谱表征了其结构,应用香草醛-冰乙酸法测定了其皂苷含量。通过1,1-二苯基-2-三硝基苯肼(DPPH)分析法和生化酶学法测定了皂苷组分水溶液的抗氧化活性和对酪氨酸酶的抑制作用。结果表明,组分S1、S2、S3均含有三萜皂苷类化合物,且质量分数分别为6.09%、34.08%、63.51%;组分S2水溶液清除DPPH自由基的能力较强(质量浓度≥5 g/L时,清除率稳定在92.5%)、抑制酪氨酸酶活性的能力较强(质量浓度为50~70 g/L时,抑制率稳定在30.4%),因而组分S2具有良好的美白抗衰老效果,可作为潜在的美白抗衰老化妆品添加剂。     

全细胞生物催化合成(R)-2-羟基-4-苯基 丁酸乙酯

以2-羰基-4-苯基丁酸乙酯(OPBE)为碳源,从葡萄园土壤中筛选分离得到一株高选择性不对称还原OPBE为(R)-2-羟基-4-苯基丁酸乙酯[(R)-HPBE]的粘质红酵母(Rhodotorula mucilaginosa CCZU-G5),利用1HNMR、GC-MS、液相色谱(LC)对产物结构进行了表征。构建了Rhodotorula mucilaginosa CCZU-G5全细胞催化还原OPBE合成(R)-HPBE的反应体系并对反应条件进行了优化。结果表明,最适催化反应条件为:在20 mL磷酸盐缓冲液(PBS)反应体系中,反应温度为35℃,pH=7.5,菌体质量浓度200 g/L,葡萄糖质量浓度30.0 g/L,金属离子Ca~(2+)浓度3 mmol/L,底物OPBE浓度为20 mmol/L,反应时间12h,在此条件下,(R)-HPBE产率达82%,对映体过量值(e.e.)为99.9%。     

Insect antifeedant properties of anthranoids from the genusVismia

Vismiones and ferruginins, representatives of a new class of lypophilic anthranoids from the genusVismia were found to inhibit feeding in larvae of species ofSpodoptera, Heliothis, and inLocusta migratoria.     

Direct observation of freeze-thaw instability of latex coatings via high pressure freezing and cryogenic SEM

Despite its industrial importance, the subject of freeze-thaw (F/T) stability of latex coatings has not been studied extensively. There is also a lack of fundamental understanding about the process and the mechanisms through which a coating becomes destabilized. High pressure (2100 bar) freezing fixes the state of water-suspended particles of polymer binder and inorganic pigments without the growth of ice crystals during freezing that produce artifacts in direct imaging scanning electron microscopy (SEM) of fracture surfaces of frozen coatings. We show that by incorporating copolymerizable functional monomers, it is possible to achieve F/T stability in polymer latexes and in low-VOC paints, as judged by the microstructures revealed by the cryogenic SEM technique. Particle coalescence as well as pigment segregation in F/T unstable systems are visualized. In order to achieve F/T stability in paints, latex particles must not flocculate and should provide protection to inorganic pigment and extender particles. Because of the unique capabilities of the cryogenic SEM, we are able to separate the effects of freezing and thawing, and study the influence of the rate of freezing and thawing on F/T stability. Destabilization can be caused by either freezing or thawing. A slow freezing process is more detrimental to F/T stability than a fast freezing process; the latter actually preserves suspension stability during freezing. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, October 27–29, 2004 in Chicago, IL. Tied for first place in The John A. Gordon Best Paper Competition.     

Ethanol and (−)-α-Pinene: Attractant Kairomones for Bark and Ambrosia Beetles in the Southeastern US

In 2002–2004, we examined the flight responses of 49 species of native and exotic bark and ambrosia beetles (Coleoptera: Scolytidae and Platypodidae) to traps baited with ethanol and/or (−)-α-pinene in the southeastern US. Eight field trials were conducted in mature pine stands in Alabama, Florida, Georgia, North Carolina, and South Carolina. Funnel traps baited with ethanol lures (release rate, about 0.6 g/day at 25–28°C) were attractive to ten species of ambrosia beetles (Ambrosiodmus tachygraphus, Anisandrus sayi, Dryoxylon onoharaensum, Monarthrum mali, Xyleborinus saxesenii, Xyleborus affinis, Xyleborus ferrugineus, Xylosandrus compactus, Xylosandrus crassiusculus, and Xylosandrus germanus) and two species of bark beetles (Cryptocarenus heveae and Hypothenemus sp.). Traps baited with (−)-α-pinene lures (release rate, 2–6 g/day at 25–28°C) were attractive to five bark beetle species (Dendroctonus terebrans, Hylastes porculus, Hylastes salebrosus, Hylastes tenuis, and Ips grandicollis) and one platypodid ambrosia beetle species (Myoplatypus flavicornis). Ethanol enhanced responses of some species (Xyleborus pubescens, H. porculus, H. salebrosus, H. tenuis, and Pityophthorus cariniceps) to traps baited with (−)-α-pinene in some locations. (−)-α-Pinene interrupted the response of some ambrosia beetle species to traps baited with ethanol, but only the response of D. onoharaensum was interrupted consistently at most locations. Of 23 species of ambrosia beetles captured in our field trials, nine were exotic and accounted for 70–97% of total catches of ambrosia beetles. Our results provide support for the continued use of separate traps baited with ethanol alone and ethanol with (−)-α-pinene to detect and monitor common bark and ambrosia beetles from the southeastern region of the US.     

Methyl 2,4,6-decatrienoates Attract Stink Bugs and Tachinid Parasitoids

Halyomorpha halys (Stål) (Pentatomidae), called the brown marmorated stink bug (BMSB), is a newly invasive species in the eastern USA that is rapidly spreading from the original point of establishment in Allentown, PA. In its native range, the BMSB is reportedly attracted to methyl (E,E,Z)-2,4,6-decatrienoate, the male-produced pheromone of another pentatomid common in eastern Asia, Plautia stali Scott. In North America, Thyanta spp. are the only pentatomids known to produce methyl 2,4,6-decatrienoate [the (E,Z,Z)-isomer] as part of their pheromones. Methyl 2,4,6-decatrienoates were field-tested in Maryland to monitor the spread of the BMSB and to explore the possibility that Thyanta spp. are an alternate host for parasitic tachinid flies that use stink bug pheromones as host-finding kairomones. Here we report the first captures of adult and nymph BMSBs in traps baited with methyl (E,E,Z)-2,4,6-decatrienoate in central Maryland and present data verifying that the tachinid, Euclytia flava (Townsend), exploits methyl (E,Z,Z)-2,4,6-decatrienoate as a kairomone. We also report the unexpected finding that various isomers of methyl 2,4,6-decatrienoate attract Acrosternum hilare (Say), although this bug apparently does not produce methyl decatrienoates. Other stink bugs and tachinids native to North America were also attracted to methyl 2,4,6-decatrienoates. These data indicate there are Heteroptera in North America in addition to Thyanta spp. that probably use methyl 2,4,6-decatrienoates as pheromones. The evidence that some pentatomids exploit the pheromones of other true bugs as kairomones to find food or to congregate as a passive defense against tachinid parasitism is discussed.     

2007～2008年世界塑料工业进展

收集了2007年7月～2008年6月世界塑料工业的相关资料,介绍了2007～2008年国外塑料工业的发展情况,提供了世界塑料产量、消费量及全球各类树脂的需求量及产能情况.按通用热塑性树脂(聚乙烯、聚丙烯、聚苯乙烯、聚氯乙烯、ABS树脂)、工程塑料(尼龙、聚碳酸酯、聚甲醛、热塑性聚酯、聚苯醚)、特种工程塑料(聚苯·硫醚、液晶聚合物、聚醚醚酮)、通用热固性树脂(酚醛、聚氨酯、不饱和聚酯树脂、环氧树脂)不同品种的顺序,对树脂的产量、消费量、供需状况及合成工艺、产品应用开发、树脂品种的延伸及应用的进一步扩展等技术作了详细介绍.     

2005～2006年国外塑料工业进展

收集了2005年7月～2006年6月国外塑料工业的相关资料,介绍了2005—2006年国外塑料工业的发展情况。提供了世界塑料产量、消费量及全球各类树脂生产量以及各国塑料制品的进出口情况。作为对比,介绍了中国塑料的生产情况。按通用热塑性树脂（聚乙烯、聚丙烯、聚苯乙烯、聚氯乙烯、ABS树脂）、工程塑料（聚酰胺、聚碳酸酯、聚甲醛、热塑性聚酯、聚苯醚）、通用热固性树脂（酚醛、聚氨酯、不饱和树脂、环氧树脂）、特种工程塑料（聚苯硫醚、液晶聚合物、聚醚醚酮）的品种顺序,对树脂的产量、消费量、供需状况及合成工艺、产品开发、树脂品种的延伸及应用的扩展作了详细的介绍。