Raman and CD spectroscopy of recombinant 68-kDa DNA human topoisomerase I and its complex with suicide DNA-substrate

N-terminally truncated recombinant 68-kDa human topoisomerase (topo) I exhibits the same DNA-driving activities as the wild-type protein. In the present study, Raman and circular dichroism techniques were employed for detailed structural characterization of the 68-kDa human topo I and its transformations induced by the suicide sequence-specific oligonucleotide (solig) binding and cleavage. Spectroscopic data combined with statistical prediction techniques were employed to construct a model of the secondary structure distribution along the primary protein structure in solution. The 68-kDa topo I was found to consist of ca. 59% alpha-helix, 24% beta-strand and/or sheets, and 17% other structures. A secondary structure transition of the 68-kDa topo I was found to accompany solig binding and cleavage. Nearly 15% of the alpha-helix of 68-kDa topo I is transferred within the other structures when in the complex with its DNA substrate. Raman spectroscopy analysis also shows redistribution of the structural rotamers of the 68-kDa topo I disulfide bonds and significant changes in the H-bonding of the Tyr residues and in the microenvironment/conformation of the Trp side chains. No structural modifications of the DNA substrate were detected by spectroscopic techniques. The data presented provide the first direct experimental evidence of the human topo I conformational transition after the cleavage step in the reaction of binding and cleavage of DNA substrate by the enzyme. This evidence supports the model of the enzyme function requiring the protein conformational transition. The most probable location of the enzyme transformations was the core and the C-terminal conservative 68-kDa topo I structural domains. By contrast, the linker domain was found to have an extremely low potential for solig-induced structural transformations. The pattern of redistribution of protein secondary structures induced by solig binding and covalent suicide complex formation supports the model of an intramolecular bipartite mode of topo I/DNA interaction in the substrate binding and cleavage reaction.     

湿氧预处理玉米秸秆酶解与酒精发酵

对湿氧预处理后的玉米秸秆酒精发酵进行了研究,并考察了预处理后纤维素及半纤维素回收率、纤维素酶解转化和酒精得率。结果表明:玉米秸秆经过湿氧预处理(195℃,15min,12×105Pa O2)后,纤维素回收率为94.6%,其中88.3%纤维素保留在滤饼中,而大部分半纤维素和木质素被溶解。滤饼利用纤维素酶处理,50℃下24 h酶解率达到了65.8%。底物质量分数为8%,经过活性干酵母142 h同步糖化发酵,酒精产量达到了理论酒精产量的75.2%。仅考虑纤维素被完全利用,相当于1 t玉米秸秆能够产生165.7 kg的酒精。     

Automatic cognitions and teen dating violence.

Objective: The present research examined whether the level of aggression in automatic cognitions was positively associated with teen dating violence after accounting for more consciously controlled, self-reported attitudes about dating violence. Method: At baseline, 95 teens who had been remanded to the juvenile court system because of antisocial behavior completed a word-completion task designed to measure the level of aggression in their automatic cognitions. Teens also completed questionnaire measures of attitudes about dating violence and dating violence perpetration during the previous three months, and then provided data on dating violence perpetration every two weeks over a 3-month follow-up period. Results: The level of aggression in automatic cognitions was positively associated with dating violence perpetration after accounting for teens' self-reported attitudes about dating violence. This pattern of results emerged with both concurrent and prospective associations. It is noteworthy that aggression in automatic cognitions also predicted changes in dating violence perpetration over the 3-month follow-up period, even after controlling for baseline levels of the perpetration of dating violence and teens' self-reported attitudes about dating violence. Conclusions: These findings suggest that theoretical models of teen dating violence should consider the role of automatic as well as more consciously controlled cognitive processes in the perpetration of teen dating violence. In addition, clinical efforts to reduce teen dating violence might benefit from targeting automatic as well as more controlled cognitive processes. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Randomized controlled trial of motivational enhancement therapy with nontreatment-seeking adolescent cannabis users: A further test of the teen marijuana check-up.

Cannabis use adversely affects adolescents and interventions that are attractive to adolescents are needed. This trial compared the effects of a brief motivational intervention for cannabis use with a brief educational feedback control and a no-assessment control. Participants were randomized into one of three treatment conditions: Motivational Enhancement Therapy (MET), Educational Feedback Control (EFC), or Delayed Feedback Control (DFC). Those who were assigned to MET and EFC were administered a computerized baseline assessment immediately following randomization and completed assessments at the 3- and 12-month follow-up periods. Participants in the DFC condition were not assessed until the 3-month follow-up. Following the completion of treatment sessions, all participants were offered up to four optional individual treatment sessions aimed at cessation of cannabis use. The research was conducted in high schools in Seattle, Washington. The participant s included 310 self-referred adolescents who smoked cannabis regularly. The main outcome measures included days of cannabis use, associated negative consequences, and engagement in additional treatment. At the 3-month follow-up, participants in both the MET and EFC conditions reported significantly fewer days of cannabis use and negative consequences compared to those in the DFC. The frequency of cannabis use was less in MET relative to EFC at 3 months, but it did not translate to differences in negative consequences. Reductions in use and problems were sustained at 12 months, but there were no differences between MET and EFC interventions. Engagement in additional treatment was minimal and did not differ by condition. Brief interventions can attract adolescent cannabis users and have positive impacts on them, but the mechanisms of the effects are yet to be identified. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Comparison of the milk-clotting properties of three plant extracts

Several proteases from plant sources have been proposed as milk coagulants, however, limited research has been done on their milk-clotting properties. The effect of temperature on the milk-clotting activity of kiwi fruit, melon and ginger extracts was evaluated, as well as the effects of the different extracts on curd properties. Melon extracts showed high milk-clotting activity over a broad temperature range (45–75 °C) while kiwi fruit and ginger extracts showed high activity over a narrower temperature range, with a maximum at 40 and 63 °C, respectively. Curds produced using kiwi extracts had textural properties comparable with those obtained using commercial rennet, while melon extracts produced a fragile gel and low curd yield. The milk-clotting behavior of the three plant extracts was related to the protease specificity present in these extracts. The kiwi proteases displayed chymosin-like properties and thus hold the best potential for use as a milk coagulant in cheese production.     

Potential Use of Quantum Dots in Flow Cytometry

QDs may offer significant advantages in environmental and bead-based applications where the target cells need to be discriminated above background fluorescence. We have examined the possible applications of QDs for flow cytometric measurements (FCM) by studying their excitation - emission spectra and their binding to paramagnetic beads. We labelled beads with either QDs or a commonly-used fluorochrome (FITC) and studied their fluorescence intensity by FCM. Flow cytometric comparisons indicated that the minimum fluorophore concentration required for detection of QDs above autofluorescent background was 100-fold less than for FITC.     

Perspectives on the role of the Society for Research on Nicotine and Tobacco in promoting global tobacco research and reducing tobacco harm.

The Society for Research on Nicotine and Tobacco (SRNT) has a critical role to play in advancing tobacco research globally. To date SRNT has sponsored a number of successful initiatives including meetings held by the society's European affiliate, establishment of the Global Network Committee in 1999, and the 2003 and 2005 global tobacco pre-conferences. The most recent SRNT conference was held for the first time outside of North America and attracted over 900 participants from 50 countries. SRNT also has sponsored workshops, provided member scholarships to researchers from low- and middle-income countries, and partnered with the World Health Organization to host www.treatobacco.net. Although these initiatives are impressive, SRNT can further support global tobacco research by (a) working with other organizations to support global tobacco science and policy (this is especially timely given the recent coming into force of the Framework Convention on Tobacco Control), (b) providing more resources including increased funding and access to online journals for those in low- and middle-income countries, (c) increasing the representation of science at world and national tobacco conferences, and (d) expanding the role of the Training Committee to place increased emphasis on mentoring tobacco scientists from low- and middle-income countries. Science will be crucial in addressing the global tobacco pandemic, and SRNT is uniquely positioned to further tobacco science and research capacity on a global basis.