Ligation of the hairpin ribozyme in cis induced by freezing and dehydration

Although reducing the temperature slows most chemical reactions, freezing can stimulate some reactions by mechanisms that are only partially understood. Here we show that freezing stimulates the self-ligation (circularization) of linear forms of the hairpin ribozyme (HPR) containing 2',3'-cyclic phosphate and 5'-OH termini. Divalent metal ions (M2+) are not required, but monovalent cations and anions at millimolar concentrations can have various effects on this reaction depending on the specific ion. Under optimal conditions, the observed rate of M2+-independent self-ligation reaches a peak (0.04 min(-1)) at -10 degrees C with a yield of -60% after 1 h. In contrast, no ligation occurs either at above 0 degrees C or in solutions that remain unfrozen when supercooled to subzero temperatures. Under freezing conditions, the cleavage-ligation equilibrium strongly favors ligation. Besides freezing, evaporation of the aqueous solvent as well as the presence of ethanol at levels of 40% or above can also induce M2+-independent HPR ligation at 25 degrees C. We argue that partial RNA dehydration, which is a common feature of freezing, evaporation, and the presence of ethanol, is a key factor supporting HPR ligation activity at both above- and below-freezing temperatures. In the context of the RNA world hypothesis, freezing-induced ligation is an attractive mechanism by which complex RNAs could have evolved under conditions in which RNA was relatively protected against degradation.     

Comparative studies on the structure and stability of fluorescent proteins EGFP, zFP506, mRFP1, "dimer2", and DsRed1

To obtain more information about the structural properties and conformational stabilities of GFP-like fluorescent proteins, we have undertaken a systematic analysis of series of green and red fluorescent proteins with different association states. The list of studied proteins includes EGFP (green monomer), zFP506 (green tetramer), mRFP1 (red monomer), "dimer2" (red dimer), and DsRed1 (red tetramer). Fluorescent and absorbance parameters, near-UV and visible CD spectra, the accessibility of the chromophores and tryptophans to acrylamide quenching, and the resistance of these proteins to the guanidine hydrochloride unfolding and kinetics of the approaching of the unfolding equilibrium have been compared. Tetrameric zFP506 was shown to be dramatically more stable than the EGFP monomer, assuming that association might contribute to the protein conformational stability. This assumption is most likely valid even though the sequences OF GFP and zPF506 are only approximately 25% identical. Interestingly, red FPs possessed comparable conformational stabilities, where monomeric mRFP1 was the most stable species under the equilibrium conditions, whereas the tetrameric DsRed1 possessed the slowest unfolding kinetics. Furthermore, EGFP is shown to be considerably less stable than mRFP1, whereas tetrameric zFP506 is the most stable species analyzed in this study. This means that the quaternary structure, being an important stabilizing factor, does not represent the only circumstance dictating the dramatic variations between fluorescent proteins in their conformational stabilities.     

Current state of epidemiologic surveillance of natural foci of plague of North Caucasus

Information on the epizootic situation in plague in the natural foci of North Caucasus and on the influence of a number of anthropogenic and natural factors on this situation is presented. The data given in this work indicate that under the conditions of the anthropogenic transformation of landscapes the character of the epizootic manifestations of plague is changed and new factors, capable of aggravating epidemiological situation, appear. In addition, some other factors must be considered, such as the insufficient financing of reliable field surveys at present, the impossibility of making reliable epizootological studies due to causes of the social character (armed conflicts), thus making it impossible to evaluate, with a sufficient degree of reliability, the real epizootic state of a number of territories and, therefore, the risk of human infection. In this connection the necessity to carefully plan prophylactic measures and measures aimed at the localization and liquidation of the probable foci of infection arises.     

On hygienic and ecological approaches in radiation protection

In this paper the problem of substantiation of one of the basic radiation protection ensurance principle is considered: sufficiency of a man radiation safety ensuring for guaranteed ensuring of radiation safety of the environment living components. This paradigm formulated in ICRP recommendations and is often referred to as hygienic or anthropocentric approach to environment radiation protection is laid down the basis of all national, including Russian, regulations in the field of radiation safety. During the last 5-10 years a lot of papers have been published, in which the hygienic principle of environmental safety ensuring is considered as a matter of dispute and the certain logical basis and the quantitative comparative estimations of human exposure doses and most irradiated vulnerable parts of nature doses are given. Change of one of the main radiation protection paradigms will demand for resolution of the enormously difficult and labor-consuming scientific problems. In the present paper, on the basis of UNSCEAR models of critical population groups dose formation and consistent application of conservativeness principle it is shown that for the ground ecosystems today there is no strong reasons for refusal of a hygienic radiation protection principle for benefit of ecological one.     

Interaction of the monoaminergic and opioidergic brain systems in the course of nociceptive and antinociceptive reactions in cats

Nociceptive responses were evoked in cats by electrical transcutaneous stimulation of the forepaw or electrical stimulation of respective brain structures; these responses could be modulated (intensified or suppressed) by combined electrical stimulation of different brain structures or by neurochemical influences upon these structures. Intensification of nociceptive responses was observed after stimulation of the noradrenergic orP-ergic systems localized in the ventral zone of the central gray (vl SGC) and the structures monosynaptically connected with the latter: the posterior and lateral hypothalamic nuclei (Hp andHl) and preoptic region (RPO). Similar effects were induced by suppression of the serotoninergic system concentrated within the dorsolateral central gray (dl SGC), dorsal raphe nucleus (Rd), and closely related structures: the ventromedial, dorsomedial, and paraventricular hypothalamic nuclei (Hvm, Hdm, andHpv), septum (Sep), basolateral amygdalar nucleus (Am bl), fields 3–4 of the hippocampus (CA3–4), and cingular cortex (GC). Suppression of the serotoninergic system resulted in a decrease in the levels of functioning of the met-enkephalin- and β-endorphinergic systems and facilitation of theP-ergic system. Moderation of nociceptive responses, i.e., an analgesic effect, was observed after either stimulation of the serotonin-, met-enkephalin-, and β-endorphinergic systems localized in thedl SGC, Rd, Hvm, Hdm, Sep, Am bl, CA3–4, andGC, or suppression of the noradrenergic system. The latter influence resulted in inhibition of theP-ergic system and a rise in the functional activity of the met-enkephalin- and β-endorphinergic systems. The composition of two antagonistic brain systems, nociceptive and antinociceptive, is considered. The antinociceptive system includes serotonin-, met-enkephalin-, and β-endorphinergic elements. Leu-enkephalin is a nonspecific activator of the met-enkephalin-, β-endorphin-, andP-ergic systems. The nociceptive system consists of thevl SGC, Hp, Hl, andRPO, while the antinociceptive system includes thedl SGC, Rd, Hvm, Hdm, Hpv, Sep, Am dl, CA3–4, andGC.     

不同施肥处理对‘赤霞珠’葡萄根际土壤养分和真菌群落的影响

【背景】宁夏贺兰山东麓葡萄产区忽视有机肥的施用,果树枝条焚烧污染环境,造成土壤养分缺失,土壤质量下降。【目的】为解决长期施用化肥对土壤造成的一系列问题,通过大田试验研究施肥及喷施不同浓度菌剂对土壤理化性质、真菌群落组成及多样性的影响,为酿酒葡萄可持续健康发展提供科学依据。【方法】以‘赤霞珠’葡萄根际土壤为试验对象,采用Illumina MiSeq高通量测序技术,测定并分析根际土壤理化性质、真菌群落组成和多样性在7个处理[常规施肥(CK)、蚯蚓粪+腐熟枝条+100倍菌剂(T1)、蚯蚓粪+腐熟枝条+200倍菌剂(T2)、蚯蚓粪+腐熟枝条+300倍菌剂(T3)、蚯蚓粪+未腐熟枝条+100倍菌剂(A1)、蚯蚓粪+未腐熟枝条+200倍菌剂(A2)和蚯蚓粪+未腐熟枝条+300倍菌剂(A3)]的变化。【结果】相较于CK,葡萄根际土壤理化性质差异明显,施肥处理增加了土壤有机质含量,土壤pH含量无明显变化,改良了土壤结构,活化了土壤有效养分。相较于CK,各处理真菌分类操作单元(operational taxonomic unit, OTU)数均降低,A2处理根际土壤丰富度及多样性均显著增加。真菌群落组成...     

Microtubules and cyclic amp in human leukocytes: on the order of things

We have shown previously that the β-adrenergic agonist isoproterenol (2μM) and the phosphodiesterase inhibitor isobutylmethylxanthine (1 mM) produce a much greater increase in cyclic AMP in human leukocytes that have been pretreated with colchicine (or with other agents that affect microtubule assembly) than in control leukocytes. The effects of colchicines were both time- and dose-dependant. These and other data suggested that the generation of cyclic AMP is normally restricted by an intact system of cytoplasmic microtubules. If so, then the same time and dose dependencies might apply to other colchicines-induced changes in leukocyte function. We have now assayed the distribution of concanavalin A (Con A)-receptor complexes on the leukocyte membrane, taking into account that leukocytes competent to assemble microtubules show a uniform distribution of surface- bound Con A whereas microtubule-deficient cells accumulate Con A in surface caps. We have found that the effect of colchicine on capping is also both time- and dose dependent, and that the dose-response relationships conform to those required to increase cyclic AMP levels. These findings provide further evidence that both colchicine-induced Con-A capping and colchicine- induced cyclic AMP generation depend upon the relaxation of constraints normally imposed by cytoplasmic microtubules upon the plasma membrane, which limit, respectively, lateral mobility of the lectin-receptor complexes, and expression of hormone-sensitive adenylate cyclase. Moreover, colchicine-induced Con-A cap formation is not affected even by very large changes in leukocyte cyclic AMP levels. Thus, elevated cyclic AMP levels do not appear to promote the dissolution of microtubules; rather, the dissolution of microtubules permits the generation of increased amounts of cyclic AMP.