Centromeric alpha satellite (AS) is composed of highly identical higher-order DNA repetitive sequences, which make the standard assembly process impossible. Because of this the AS repeats were severely underrepresented in previous versions of the human genome assembly showing large centromeric gaps. The latest hg38 assembly (GCA_000001405.15) employed a novel method of approximate representation of these sequences using AS reference models to fill the gaps. Therefore, a lot more of assembled AS became available for genomic analysis. We used the PERCON program previously described by us to annotate various suprachromosomal families (SFs) of AS in the hg38 assembly and presented the results of our primary analysis as an easy-to-read track for the UCSC Genome Browser. The monomeric classes, characteristic of the five known SFs, were color-coded, which allowed quick visual assessment of AS composition in whole multi-megabase centromeres down to each individual AS monomer. Such comprehensive annotation of AS in the human genome assembly was performed for the first time. It showed the expected prevalence of the known major types of AS organization characteristic of the five established SFs. Also, some less common types of AS arrays were identified, such as pure R2 domains in SF5, apparent J/R and D/R mixes in SF1 and SF2, and several different SF4 higher-order repeats among reference models and in regular contigs. No new SFs or large unclassed AS domains were discovered. The dataset reveals the architecture of human centromeres and allows classification of AS sequence reads by alignment to the annotated hg38 assembly. The data were deposited here: http://genome.ucsc.edu/cgi-bin/hgTracks?db=hg38&hgt.customText=https://dl.dropboxusercontent.com/u/22994534/AS-tracks/human-GRC-hg38-M1SFs.bed.bz2.
A new kinetic model of enzymatic catalysis is proposed, which postulates that enzyme solutions are equilibrium systems of oligomers differing in the number of subunits and in the mode of their assembly. It is suggested that the catalytic and regulatory sites of allosteric enzymes are of composite nature and appear as a result of subunits joining. Two possible joining modes are postulated at each oligomerization step. Catalytic site may arise on oligomer formed only by one of these modes. Effector acts by fastening together components of certain oligomeric form and increases the life time of this form. It leads to a shift of oligomer equilibrium and increases a proportion of effector-binding oligomers. Effectors-activators bind the oligomers carrying composite catalytic sites and effectors-inhibitors bind the oligomers, which do not carry active catalytic sites. Thus, catalytic activity control in such system is explained by effector-induced changes of a catalytic sites number, but not of a catalytic site activity caused by changes of subunit's tertiary structure. The postulates of the model do not contradict available experimental data and lead to a new type of general rate equation, which allows to describe and understand the specific kinetic behavior of allosteric enzymes as well as Michaelis type enzymes. All known rate equations of allosteric The equation was tested by modeling the kinetics of human erythrocyte phosphofructokinase. It enabled to reproduce quantitatively the 66 kinetic curves experimentally obtained for this enzyme under different reaction conditions.
In a series of the experiments at different time-of-flight spectrometers of
heavy ions we have observed manifestations of a new at least ternary decay
channel of low excited heavy nuclei. Due to specific features of the effect, it
was called collinear cluster tri-partition (CCT). The experimental results
obtained initiated a number of theoretical articles dedicated to different
aspects of the CCT. We compare theoretical predictions with our experimental
data, only partially published so far. The model of one of the most populated
CCT modes that gives rise to the so called "Ni-bump" is discussed. Detection of
the 68-72Ni fission fragments with a kinetic energy E<25 MeV at the
mass-separator Lohengrin is proposed for an independent experimental
verification of the CCT.Comment: 16 pages, 14 figure
The receptive fields of the sensorimotor cortex neurons identified by electrocutaneous stimulation were modified by microelectrophoretically applied picrotoxin which is known to reduce inhibition. a relatively short application of picrotoxin (90 nA during 3-6 min) markedly increased the size of the neuronal receptive fields in the sensorimotor cortex. Control application of glutamate showed that additional depolarization did not affect receptive fields of the spontaneously active units. Our results together with other work in this field further support the hypothesis that inhibitory processes play a major role in forming functional properties of the cerebral cortex neurons.
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