Hyeyoung Kim

© 2015 Walker et al.Background: Carbohydrate binding modules bind polysaccharides and help target glycoside hydrolases catalytic domains to their appropriate carbohydrate substrates. To better understand how CBMs can improve cellulolytic enzyme reactivity, representatives from each of the 18 families of CBM found in Ruminoclostridium thermocellum were fused to the multifunctional GH5 catalytic domain of CelE, which can hydrolyze numerous types of polysaccharides including cellulose, mannan, and xylan. Since CelE is a cellulosomal enzyme, none of these fusions to a CBM previously existed. Results: CelEcc-CBM fusions were assayed for their ability to hydrolyze cellulose, lichenan, xylan, and mannan. Several CelEcc-CBM fusions showed enhanced hydrolytic activity with different substrates relative to the fusion to CBM3a from the cellulosome scaffoldin, which has high affinity for binding to crystalline cellulose. Additional binding studies and quantitative catalysis studies using nanostructure-initiator mass spectrometry were carried out with the CBM3a, CBM6, CBM30, and CBM44 fusion enzymes. In general, and consistent with observations of others, enhanced enzyme reactivity was correlated with moderate binding affinity of the CBM. Numerical analysis of reaction time courses showed that CelEcc-CBM44, a combination of a multifunctional enzyme domain with a CBM having broad binding specificity, gave the fastest rates for hydrolysis of both the hexose and pentose fractions of ionic-liquid pretreated switchgrass. Conclusion: We have shown that fusions of different CBMs to a single multifunctional GH5 catalytic domain can increase its rate of reaction with different pure polysaccharides and with pretreated biomass. This fusion approach, incorporating domains with broad specificity for binding and catalysis, provides a new avenue to improve reactivity of simple combinations of enzymes within the complexity of plant biomass.

© 2015. American Geophysical Union. All Rights Reserved. The impacts of droughts on the Amazon ecosystem have been broadly discussed in recent years, but a comprehensive understanding of the consequences is still missing. In this study, we show evidence of a fragile hydrological equilibrium in the western Amazon. While drainage systems located near the equator and the western Amazon do not show water deficit in years with average climate conditions, this equilibrium can be broken during drought events. More importantly, we show that this effect is persistent, taking years until the normal hydrological patterns are reestablished. We show clear links between persistent changes in forest canopy structure and changes in hydrological patterns, revealing physical evidence of hydrological mechanisms that may lead to permanent changes in parts of the Amazon ecosystem. If prospects of increasing drought frequency are confirmed, a change in the current hydroecological patterns in the western Amazon could take place in less than a decade.

Shift work and overtime have been implicated as important work-related risk factors for cardiovascular disease. Many firefighters who contractually work on a 24-hr work schedule, often do overtime which can result in working multiple, consecutive 24-hr shifts. Very little research has been conducted on firefighters at work that examines the impact of performing consecutive 24-hr shifts on cardiovascular physiology. Also, there have been no standard field methods for assessing in firefighters the cardiovascular changes that result from 24-hr shifts, what we call "cardiovascular strain". The objective of this study, as the first step toward elucidating the role of very long shifts in the development of CVD in firefighters, is to develop and describe a theoretical framework for studying cardiovascular strain in firefighters on very long shifts. The developed theoretical framework was built on an extensive literature review, our recently completed studies with firefighters in Southern California, e-mail and discussions with several firefighters on their experiences of consecutive shifts, and our recently conducted feasibility study in a small group of firefighters of several ambulatory cardiovascular strain biomarkers. The theoretical framework developed in this study will facilitate future field studies on consecutive 24-hr shifts and cardiovascular health in firefighters. Also it will increase our understanding of the mechanisms by which shift work or long work hours can affect CVD, particularly through CVD biological risk factors, and thereby inform policy about sustainable work and rest schedules for firefighters.

이 글의 목적은 부르디외의 ‘하비투스’ 개념에 제기되는 결정론의 의혹을 ‘기호적 창발’의 구조로 완화함으로써, 상징권력의 구조에 관한 자연주의적 탐구의 가능성을 제안하는 데 있다. 부르디외의 상징권력에는 하비투스의 이중성 즉, ‘구조화하는 구조’와 ‘구조화된 구조’의 논리가 내재되어 있는데, 그 이중성은 증여와 언어교환의 경험을 통해 확인될 수 있다. 그러나 하비투스의 이중적인 실천 논리가 함축하는 구조적 제약성과 그 작용 과정의 불투명성으로 인해, 아처나 킹과 같은 사회학자들은 부르디외의 사회학이 여전히 결정론 또는 유물론의 시각을 보여 준다고 분석한다. 이 문제에 필자는 하비투스의 제약성은 ‘몸’을 가진 유기체가 세계와 상호작용함으로써 반복적으로 경험하는 패턴들을 구조화하는 과정에서 드러나는 유연한 도식이라고 밝힌다. 이 글은 그 해명의 과정을 체험주의의 ‘영상도식’과 ‘기호적 창발’의 구조로 밝혀, 부르디외의 하비투스 개념에 제기되는 결정론에 대한 의혹을 완화하고, 상징권력에 관한 자연주의적인 탐구의 가능성을 보인다.