184 research outputs found
Number of natively unfolded proteins scales with genome size
Natively unfolded proteins exist as an ensemble of flexible conformations
lacking a well defined tertiary structure along a large portion of their
polypeptide chain. Despite the absence of a stable configuration, they are
involved in important cellular processes. In this work we used from three
indicators of folding status, derived from the analysis of mean packing and
mean contact energy of a protein sequence as well as from VSL2, a disorder
predictor, and we combined them into a consensus score to identify natively
unfolded proteins in several genomes from Archaea, Bacteria and Eukarya. We
found a high correlation among the number of predicted natively unfolded
proteins and the number of proteins in the genomes. More specifically, the
number of natively unfolded proteins scaled with the number of proteins in the
genomes, with exponent 1.81 +- 0.10. This scaling law may be important to
understand the relation between the number of natively unfolded proteins and
their roles in cellular processes.Comment: Submitted to Biophysics and Bioengineering Letters
http://padis2.uniroma1.it:81/ojs/index.php/CISB-BB
Transfer of metal ions in the soil-root interface: influence of copper(II) on the stability of the fibrils
A network of Ca-polygalacturonate arranged in fibrils
similar to those of plant roots (Gessa C. and Deiana
S., (1990); C.Gessa and Deiana S., (1990)) constitutes
a very useful model far the study of the ionic transfer
both in the soil-root interface and in the apoplast.
Due to the fact that important properties of the network, such as the hydration degree and the absorption phenomena, vary dramatically with the reticulating ion (Gessa C. and Deiana S., (1989)), this note reports on the influence of the metal ions on the fibrillar structure of the network and gives further information about the transfer of the metal ions to the roots
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Codon Bias Patterns of 's Interacting Proteins
Synonymous codons, i.e., DNA nucleotide triplets coding for the same amino
acid, are used differently across the variety of living organisms. The
biological meaning of this phenomenon, known as codon usage bias, is still
controversial. In order to shed light on this point, we propose a new codon
bias index, , that is based on the competition between cognate and
near-cognate tRNAs during translation, without being tuned to the usage bias of
highly expressed genes. We perform a genome-wide evaluation of codon bias for
, comparing with other widely used indices: , , and
. We show that and capture similar information by being
positively correlated with gene conservation, measured by ERI, and
essentiality, whereas, and appear to be less sensitive to
evolutionary-functional parameters. Notably, the rate of variation of and
with ERI allows to obtain sets of genes that consistently belong to
specific clusters of orthologous genes (COGs). We also investigate the
correlation of codon bias at the genomic level with the network features of
protein-protein interactions in . We find that the most densely
connected communities of the network share a similar level of codon bias (as
measured by and ). Conversely, a small difference in codon bias
between two genes is, statistically, a prerequisite for the corresponding
proteins to interact. Importantly, among all codon bias indices, turns
out to have the most coherent distribution over the communities of the
interactome, pointing to the significance of competition among cognate and
near-cognate tRNAs for explaining codon usage adaptation
Effects of Al substitution on goethite formation
Goethites containing up to 32.7 mole % Al were synthesized and characterized through diffractometry,
spectrometry, DSC and chemical techniques. Results indicate that crystal growth was favoured or hindered depending on the percentage of aluminum incorporated into the structure. Goethites to which 5-10 mole % Al were initially added crystallized best, as shown by the highest crystallite dimensions calculated from X-ray and Mössbauer analyses, and by the lowest surface areas values. Over such substitution degree goethite crystallization was hindered and for sample synthesized in presence of 40 mole % Al the
separation of a discrete amount of gibbsite and bayerite occurred.
Both crystallinity and Al-substitution degree influenced the goethite dehydroxylation endothermic peak
temperature playing a competitive action in the peak shift. In fact, the increase in the thermal stability induced by the presence of Al3+ ions into the structure was counteracted by the decrease due to the particle size reduction.
The stabilizing effect of aluminum was confirmed by the oxalate treatment which removed from the Al-free
sample a Fe amount higher than that from the sample containing about 20 mole % Al, although both
had similar crystallinity
Transfer of metal ions at the soil-root interface: role of VO<sup>2+</sup> on Fe<sup>3+</sup> mobilization from a Fe(III)-network
This note reports the role of VO(IV) on Fe(III) mobilization from a Fe(III)-polygalacturonate network. The effect of the reaction on the physical properties of the system is also considered
Role of the polygalacturonate network on the iron (III) reduction by caffeic acid
This communication reports the role of polygalacturonate network on the Fe(III) reduction by caffeic acid. The effect of phosphate ions on the redox reaction is also considered
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