Studies On The Cross Strand Hydrogen Bonds In DNA Double Helices

Abstract

A systematic analysis has been carried out to examine all the stereochemically possible bifurcated hydrogen bonds including those of cross strand type between propeller twisted base pairs in DNA double helices by stereochemical considerations involving base pairs alone and by molecular mechanics studies on dimer and trimer duplexes. The results show that there are limited number of combinations of adjacent base pairs that would facilitate bifurcated cross- strand hydrogen bond (CSH). B-type helices concomitant with negative propeller twist seem to be more favored for the occurrence of CSH than canonical A-type helices because of slide in the latter. The results also demonstrate that helices with appropriate sequences may possess continuous run of these propeller twist driven cross strand hydrogen bonds indicating that they may infact be considered as yet another general structural feature of DNA helices.     

The self-morningness/eveningness (Self-ME): An extremely concise and totally subjective assessment of diurnal preference

The assessment of diurnal preference, or the preferred timing of sleep and activity, is generally based on comprehensive questionnaires such as the Horne–Östberg (HÖ). The aim of the present study was to assess the reliability of a subject’s self-classification as extremely morning (Self-MM), more morning than evening (Self-M), more evening than morning (Self-E) or extremely evening (Self-EE) type, based on the last question of the HÖ (Self-ME). A convenience sample of 461 subjects [23.8?±?4.7 years; 322 females] completed a full sleep–wake assessment, including diurnal preference (HÖ), night sleep quality (Pittsburgh Sleep Quality Index, PSQI), daytime sleepiness (Karolinska Sleepiness Scale, KSS), and habitual sleep–wake timing (12?d sleep diaries; n?=?296). Significant differences in HÖ total score were observed between Self-ME classes, with each class being significantly different from neighboring classes (p?<?0.0001). Significant differences in sleep–wake timing (bed time, try to sleep and sleep onset, wake up, and get up time) were observed between Self-ME classes. Such differences were maintained when sleep–wake habits were analysed separately on work and free days, and also in a smaller group of 67 subjects who completed the Self-ME as a stand-alone rather than as part of the original questionnaire. Significant differences were observed in the time-course of subjective sleepiness by Self-ME class in both the large and the small group, with Self-MM and Self-M subjects being significantly more alert in the morning and sleepier in the evening hours compared with their Self-E and Self-EE counterparts. Finally, significant differences were observed in night sleep quality between Self-ME classes, with Self-EE/Self-E subjects sleeping worse than their Self-MM/Self-M counterparts, and averaging just over the abnormality PSQI threshold of 5. In conclusion, young, healthy adults can define their diurnal preference based on a single question (Self-ME) in a way that reflects their sleep–wake timing, their sleepiness levels over the daytime hours, and their night sleep quality. Validation of the Self-ME across the decades and in diseased populations seems worthy.     

Turkish nationalism and the Kurdish question

This article addresses the ways in which Turkish nationalism has perceived the Kurdish question. It is shown that both Turkish nationalism and the Kurdish question have passed through some paradigmatic moments in the twentieth century. This, I argue, has shaped the way that the Kurdish question has been perceived by Turkish nationalism. While the Kurdish question had been seen by Turkish nationalism mostly in terms of a fatal rivalry between the backward, pre-modern and tribal past and the prosperous present in the first half of the century, it was perceived in terms of a tension between the peripheral economy and national market in the fifties and sixties. In the 1970s, the Kurdish unrest was believed to be a product of communist incitement. Despite this impurity in perception, one thing has remained nearly unchanged for Turkish nationalism: Kurds could become Turkish. In other words, Turkish nationalism of the republican era has principally perceived Kurds as future-Turks. However, the signs in circulation at present indicate that the confidence of Turkish nationalism as to Kurds’ potential of becoming Turkish is not as firm as it used to be. At present, Turkish nationalism seems to be getting prepared to abandon its contention that Kurds are future-Turks.     

A critical note on ‘exclusive recognition’

Cenk Saracoglu conceptualizes the antipathy towards Kurdish migrants manifesting in certain cities of Turkey since the early 2000s as ‘exclusive recognition’ in his article ‘“Exclusive recognition”: the new dimensions of the question of ethnicity and nationalism in Turkey’ published in Ethnic and Racial Studies 32(4). According to the author, these recent developments represent ‘a historically specific ethnicization process’ and its sources cannot be found directly and only in historical discourses and policy of mainstream Turkish nationalism. In this note, I contradict the author's claims by asserting that the recent manifestations of anti-Kurdish sentiments are an extension of the ongoing policies of Turkish national identity based on Turkish nationalism.     

Good student questions in inquiry learning

Acquisition of scientific reasoning is one of the big challenges in education. A popular educational strategy advocated for acquiring deep knowledge is inquiry-based learning, which is driven by emerging ‘good questions’. This study will address the question: ‘Which design features allow learners to refine questions while preserving student ownership of the inquiry process?’ This design-based research has been conducted over several years with advanced high-school biology classes. The results confirm the central role of question elaboration as an interactive process that leads from vague to complex and adequate. To make this happen, the inquiry process must extend over a long time, learners and teachers should share a knowledge improvement goal, and text produced by students should be structured by question–answer pairs addressing a single concept using authentic resources. Further features are discussion with peers, teacher feedback with respect to answer elaboration and conceptual differentiation, and finally, teacher guidance that should fade out in successive inquiry cycles to ensure student responsibility.     

Elements of episodic-like memory in animal models

Representations of unique events from one’s past constitute the content of episodic memories. A number of studies with non-human animals have revealed that animals remember specific episodes from their past (referred to as episodic-like memory). The development of animal models of memory holds enormous potential for gaining insight into the biological bases of human memory. Specifically, given the extensive knowledge of the rodent brain, the development of rodent models of episodic memory would open new opportunities to explore the neuroanatomical, neurochemical, neurophysiological, and molecular mechanisms of memory. Development of such animal models holds enormous potential for studying functional changes in episodic memory in animal models of Alzheimer’s disease, amnesia, and other human memory pathologies. This article reviews several approaches that have been used to assess episodic-like memory in animals. The approaches reviewed include the discrimination of what, where, and when in a radial arm maze, dissociation of recollection and familiarity, object recognition, binding, unexpected questions, and anticipation of a reproductive state. The diversity of approaches may promote the development of converging lines of evidence on the difficult problem of assessing episodic-like memory in animals.     

四川白水河自然保护区问题分析排序与对策研究

以白水河国家级自然保护区为研究对象,采用“问题树模型”、“对策树模型”和“距阵排序”等分析工具,对白水河自然保护区过去存在的问题进行分析与评价,并提出了白水河自然保护区的具体保护管理对策。     

‘Are we all secular/ized yet?’: reflections on David Goldberg’s ‘Are we all post-racial yet?’

ABSTRACT

This paper expands upon some of Goldberg’s initial reflections regarding the new type of ‘subject’ that is at the heart of post-raciality. A particular attention is paid to the connection with religion, as many of the current conflicts in Europe have been articulated through the grammar of secularism and religion, especially in relationship to Islam. This observation invites us to consider how this ‘racialization of religion’ figures as a reminder of the central role of this politico-theological question in the demarcation of who counts as a proper (political) subject, and how the current debates about Islam figure as a reminder of that.     

Introduction: Have hunter-gatherers ever lived in tropical rain forest independently of agriculture?

It has often been assumed that peoples living today as foragers in tropical rain forests are remnants of paleolithic populations that have been subsisting in their forest habitats for millennia and have only recently come into contact with sources of domesticated plants and animals. Independently, the two of us have published articles that challenge this view and propose the hypothesis that hunter- gatherers could never have lived in tropical rain forest without direct or indirect access to cultivated foods. This article serves as an introduction to six articles in this issue of Human Ecology, all devoted to this hypothesis. To provide background for this journal's readers, we summarize here our original articles.