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Regular version of the site
Of all publications in the section: 646
by name
by year
Leon-Zayas R., Novotny M., Podell S. et al. Applied and Environmental Microbiology. 2015. Vol. 81. No. 24. P. 8265-8276.

Hadal ecosystems are found at a depth of 6,000 m below sea level and below, occupying less than 1% of the total area of the ocean. The microbial communities and metabolic potential in these ecosystems are largely uncharacterized. Here, we present four single amplified genomes (SAGs) obtained from 8,219 m below the sea surface within the hadal ecosystem of the Puerto Rico Trench (PRT). These SAGs are derived from members of deep-sea clades, including the Thaumarchaeota and SAR11 clade, and two are related to previously isolated piezophilic (high-pressure-adapted) microorganisms. In order to identify genes that might play a role in adaptation to deep-sea environments, comparative analyses were performed with genomes from closely related shallow-water microbes. The archaeal SAG possesses genes associated with mixotrophy, including lipoylation and the glycine cleavage pathway. The SAR11 SAG encodes glycolytic enzymes previously reported to be missing from this abundant and cosmopolitan group. The other SAGs, which are related to piezophilic isolates, possess genes that may supplement energy demands through the oxidation of hydrogen or the reduction of nitrous oxide. We found evidence for potential trench-specific gene distributions, as several SAG genes were observed only in a PRT metagenome and not in shallower deep-sea metagenomes. These results illustrate new ecotype features that might perform important roles in the adaptation of microorganisms to life in hadal environments.

Added: Feb 23, 2017
Silva B. F., Fedorova N., Levit V. et al. Revista Brasileira de Meteorologia. 2012. Vol. 26. No. 3. P. 287-294.
Structures of meteorological systems, associated with heavy precipitation in the Alagoas State, for the 2003-2006 period were studied. Infrared satellite images, reanalysis data products of the National Centers for Environmental Prediction (NCEP) and data from seventeen Alagoas pluviometric stations were used. The goal of this study is the analysis of the heavy precipitation causes and determination of the associated weather systems. Heavy precipitations were usually registered during autumn/ winter seasons. Also, half of all spring/summer heavy precipitations events occurred in January. Wave Disturbances in the Trade Winds, Brazilian Northeast Jet Streams and Cold Front Extremities were associated with heavy precipitations. Almost all heavy precipitations events were connected with Mesoscale Convective Complexes in the west region of the State and usually did not occur in the east region. To exemplify the used analysis method a case study is discussed.
Added: Oct 4, 2012
Kuzminov I. Regional Research of Russia. 2011. No. 1. P. 41-51.


This article defines the framework for identifying social and economic challenges that the timber industry currently faces in the regions of Northern European Russia. The analysis of identified problems on a regional and local scale for the case of Kostroma oblast is presented. The main institutional shifts during the

1990s–2000s are discussed, along with economic problems of regional timber industry systems and their social implications, as well as how companies and rural communities of Kostroma oblast have adapted to the challenges of the ongoing economic recession in 2009.

Added: Sep 30, 2012
Minin A. A. Biology Bulletin Reviews. 2012. Vol. 2. No. 2. P. 176-182.

Issues of interrelations between climate and land ecosystems (mainly, their basic component: vegetative land cover) are considered in the paper. The hysteresis effect, which manifests itself in the dynamics of biome boundaries, is described on both a global and a regional scale and based on data analysis of the primary production of aboveground phytomass and evaporability. The work helps reveal centers of interannual stability of the onset of phenological events throughout the territory of European Russia and study regularities in their shifts during the vegetation period. The interannual temporal variability in the onset of natural events is shown to remain within the range of climatic variables. It is established that the temporal patterns for the onset of many spring events have advanced to earlier dates over the past decades (whereas those for autumn events have shifted to later dates) and the vegetation periods have extended, e.g., by more than ten additional days in the northern part of European Russia. However, phenological responses to global warming show differences across regions and groups of organisms, which evidences that the biota responds as a whole to presentday climate changes in different ways.

Added: Oct 17, 2014
Косов А., Чернышов А. А., Могилевский М. и др. Izvestiya, Atmospheric and Oceanic Physics. 2018. № 9. С. 1282-1290.

This paper describes a space experiment that is planned to be performed within the framework of the Russian project of the microsatellite CHIBIS AI to meaure ionospheric signal delays to determine the electron density and spatial fluctuations of the ionospheric and magnetospheric plasma. The measurements will be conducted by the phase interferometer method at two levels using signals from the onboard in-phase transmitters and GPS/GLONASS signals. The location of the radiation sources at two levels will make it possible to separate plasma variations in the ionosphere and inner magnetosphere-plasmasphere. The experimental results are of interest both for solving fundamental problems of near-Earth plasma physics and applied problems to improve positioning accuracy using global navigation systems.

Added: Nov 28, 2019
Kosov A., Chenyshov A., Mogilevsky M. и др. Izvestiya, Atmospheric and Oceanic Physics. 2018. Т. 54. № 9. С. 1282-1290.

This paper describes a space experiment that is planned to be performed within the framework of

the Russian project of the microsatellite CHIBIS AI to meaure ionospheric signal delays to determine the

electron density and spatial fluctuations of the ionospheric and magnetospheric plasma. The measurements

will be conducted by the phase interferometer method at two levels using signals from the onboard in-phase

transmitters and GPS/GLONASS signals. The location of the radiation sources at two levels will make it pos-

sible to separate plasma variations in the ionosphere and inner magnetosphere–plasmasphere. The experi-

mental results are of interest both for solving fundamental problems of near-Earth plasma physics and applied

problems to improve positioning accuracy using global navigation systems.

Added: Feb 18, 2019
Bankevich A., Nurk S., Antipov D. et al. Journal of Computational Biology. 2012. Vol. 19. No. 5. P. 455-477.

The lion's share of bacteria in various environments cannot be cloned in the laboratory and thus cannot be sequenced using existing technologies. A major goal of single-cell genomics is to complement gene-centric metagenomic data with whole-genome assemblies of uncultivated organisms. Assembly of single-cell data is challenging because of highly non-uniform read coverage as well as elevated levels of sequencing errors and chimeric reads. We describe SPAdes, a new assembler for both single-cell and standard (multicell) assembly, and demonstrate that it improves on the recently released E+V−SC assembler (specialized for single-cell data) and on popular assemblers Velvet and SoapDeNovo (for multicell data). SPAdes generates single-cell assemblies, providing information about genomes of uncultivatable bacteria that vastly exceeds what may be obtained via traditional metagenomics studies. SPAdes is available online (http://bioinf.spbau.ru/spades). It is distributed as open source software.

Added: Feb 13, 2013
Кузин И. А. Вестник Московского университета. Серия 7: Философия. 2015. № 3. С. 3-18.

The commented famous work by S.J. Gould and R.C. Lewontin is crucial not only to sociobiology critique but to polemics on evolutionary theory in general. Reflection provoked by Gould and Lewontin’s paper in the field of philosophy of biology enables to clarify the relation between the adaptationist program and biological reductionism.

Added: Oct 19, 2016
Karachurina L. B., Mkrtchyan N. V. Demografia. 2012. Vol. 55. No. 5. P. 61-88.

The paper analyses the patterns of demographic dynamics of settlements and districts of various types in Russia within the framework of the core-periphery model. We test the hypotheses stating that population density is growing in regional centres and in their surroundings; variations in the dynamics of population growth (and its components) within regions are not less prominent than those between regions; differences between peripheral territories are less significant than those between re-gional centres, and these are the differences which define socio-economic inequality of the regions. The paper also looks into the dynamics of population growth in cities, district centres and rural settlements in relation to the proximity of an administrative unit to a regional centre.

Added: Oct 16, 2014
Hyafil A., Fontolan L., Kabdebon C. et al. eLife. 2015. No. 4. P. 1-45.

Many environmental stimuli present a quasi-rhythmic structure at different timescales that the brain needs to decompose and integrate. Cortical oscillations have been proposed as instruments of sensory de-multiplexing, i.e., the parallel processing of different frequency streams in sensory signals. Yet their causal role in such a process has never been demonstrated. Here, we used a neural microcircuit model to address whether coupled theta–gamma oscillations, as observed in human auditory cortex, could underpin the multiscale sensory analysis of speech. We show that, in continuous speech, theta oscillations can flexibly track the syllabic rhythm and temporally organize the phoneme-level response of gamma neurons into a code that enables syllable identification. The tracking of slow speech fluctuations by theta oscillations, and its coupling to gamma-spiking activity both appeared as critical features for accurate speech encoding. These results demonstrate that cortical oscillations can be a key instrument of speech de-multiplexing, parsing, and encoding.

Added: Jul 15, 2015
Nechaev S., Tamm M., Nazarov L. et al. Soft Matter. 2015. Vol. 11. No. 5. P. 1019-1025.

A statistical model describing a fine structure of the intra-chromosome maps obtained by a genome-wide chromosome conformation capture method (Hi-C) is proposed. It combines hierarchical chain folding with quenched heteropolymer structure of primary chromatin sequences. It is conjectured that the observed Hi-C maps are statistical averages over many different ways of hierarchical genome folding. It is shown that the existence of quenched primary structure coupled with hierarchical folding induces full range of features observed in experimental Hi-C maps: hierarchical elements, chess-board intermittency and large-scale compartmentalization

Added: Oct 23, 2014
Iscan Z., Nikulin V. Plos One. 2018. Vol. 13. No. 1. P. 1-17.

Brain-computer interface (BCI) paradigms are usually tested when environmental and biological artifacts are intentionally avoided. In this study, we deliberately introduced different perturbations in order to test the robustness of a steady state visual evoked potential (SSVEP) based BCI. Specifically we investigated to what extent a drop in performance is related to the degraded quality of EEG signals or rather due to increased cognitive load. In the online tasks, subjects focused on one of the four circles and gave feedback on the correctness of the classification under four conditions randomized across subjects: Control (no perturbation), Speaking (counting loudly and repeatedly from one to ten), Thinking (mentally counting repeatedly from one to ten), and Listening (listening to verbal counting from one to ten). Decision tree, Naïve Bayes and K-Nearest Neighbor classifiers were used to evaluate the classification performance using features generated by canonical correlation analysis. During the online condition, Speaking and Thinking decreased moderately the mean classification accuracy compared to Control condition whereas there was no significant difference between Listening and Control conditions across subjects. The performances were sensitive to the classification method and to the perturbation conditions. We have not observed significant artifacts in EEG during perturbations in the frequency range of interest except in theta band. Therefore we concluded that the drop in the performance is likely to have a cognitive origin. During the Listening condition relative alpha power in a broad area including central and temporal regions primarily over the left hemisphere correlated negatively with the performance thus most likely indicating active suppression of the distracting presentation of the playback. This is the first study that systematically evaluates the effects of natural artifacts (i.e. mental, verbal and audio perturbations) on SSVEP-based BCIs. The results can be used to improve individual classification performance taking into account effects of perturbations.

Added: Oct 30, 2018
Kozlov A., Vershubsky G., Kozlova M. A. International Journal of Circumpolar Health. 2003. No. 62:2. P. 158-166.

Objectives. Arterial blood pressure and serum blood glucose con­centration, and the level of anxiety, as determined by the Spielberger test, as physical and psychological markers of stress under “moderni­zation”, were studied in groups of native Siberians: the Khanty and the Mansi.

Results. The fraction of respondents with a high level of anxiety is 64% of the total sample. The average values of systolic and diastolic blood pressure are higher among natives living in large than in small “national” settlements (p<0.05). The arterial blood pressure of town dwellers is even higher. The same patterns are seen in the blood se­rum glucose concentrations in female samples. The average arterial blood pressure (in males and females) and the blood serum glucose concentration (in females) increases as people diverge from “tradi­tional” lifestyles.

Conclusions. The results demonstrate that “modernization” and urbanization have a serious stressing influence on the aborigines of North Siberia.

Added: Dec 26, 2012
Vlassov V. Neuro-epidemiology. 2015. Vol. 45. No. 3. P. 190-202.

Background: Recent evidence suggests that stroke is increasing as a cause of morbidity and mortality in younger adults, where it carries particular significance for working individuals. Accurate and up-to-date estimates of stroke burden are important for planning stroke prevention and management in younger adults. Objectives: This study aims to estimate prevalence, mortality and disability-adjusted life years (DALYs) and their trends for total, ischemic stroke (IS) and hemorrhagic stroke (HS) in the world for 1990-2013 in adults aged 20-64 years. Methodology: Stroke prevalence, mortality and DALYs were estimated using the Global Burden of Disease (GBD) 2013 methods. All available data on rates of stroke incidence, excess mortality, prevalence and death were collected. Statistical models were used along with country-level covariates to estimate country-specific stroke burden. Stroke-specific disability weights were used to compute years lived with disability and DALYs. Means and 95% uncertainty intervals (UIs) were calculated for prevalence, mortality and DALYs. The median of the percent change and 95% UI were determined for the period from 1990 to 2013. Results: In 2013, in younger adults aged 20-64 years, the global prevalence of HS was 3,725,085 cases (95% UI 3,548,098-3,871,018) and IS was 7,258,216 cases (95% UI 6,996,272-7,569,403). Globally, between 1990 and 2013, there were significant increases in absolute numbers and prevalence rates of both HS and IS for younger adults. There were 1,483,707 (95% UI 1,340,579-1,658,929) stroke deaths globally among younger adults but the number of deaths from HS (1,047,735 (95% UI 945,087-1,184,192)) was significantly higher than the number of deaths from IS (435,972 (95% UI 354,018-504,656)). There was a 20.1% (95% UI -23.6 to -10.3) decline in the number of total stroke deaths among younger adults in developed countries but a 36.7% (95% UI 26.3-48.5) increase in developing countries. Death rates for all strokes among younger adults declined significantly in developing countries from 47 (95% UI 42.6-51.7) in 1990 to 39 (95% UI 35.0-43.8) in 2013. Death rates for all strokes among younger adults also declined significantly in developed countries from 33.3 (95% UI 29.8-37.0) in 1990 to 23.5 (95% UI 21.1-26.9) in 2013. A significant decrease in HS death rates for younger adults was seen only in developed countries between 1990 and 2013 (19.8 (95% UI 16.9-22.6) and 13.7 (95% UI 12.1-15.9)) per 100,000). No significant change was detected in IS death rates among younger adults. The total DALYs from all strokes in those aged 20-64 years was 51,429,440 (95% UI 46,561,382-57,320,085). Globally, there was a 24.4% (95% UI 16.6-33.8) increase in total DALY numbers for this age group, with a 20% (95% UI 11.7-31.1) and 37.3% (95% UI 23.4-52.2) increase in HS and IS numbers, respectively. Conclusions: Between 1990 and 2013, there were significant increases in prevalent cases, total deaths and DALYs due to HS and IS in younger adults aged 20-64 years. Death and DALY rates declined in both developed and developing countries but a significant increase in absolute numbers of stroke deaths among younger adults was detected in developing countries. Most of the burden of stroke was in developing countries. In 2013, the greatest burden of stroke among younger adults was due to HS. While the trends in declining death and DALY rates in developing countries are encouraging, these regions still fall far behind those of developed regions of the world. A more aggressive approach toward primary prevention and increased access to adequate healthcare services for stroke is required to substantially narrow these disparities.

Added: Oct 29, 2015
Vlassov V. Neuro-epidemiology. 2015. Vol. 45. No. 3. P. 177-189.

Background: There is increasing recognition of stroke as an important contributor to childhood morbidity and mortality. Current estimates of global childhood stroke burden and its temporal trends are sparse. Accurate and up-to-date estimates of childhood stroke burden are important for planning research and the resulting evidence-based strategies for stroke prevention and management. Objectives: To estimate the prevalence, mortality and disability-adjusted life years (DALYs) for ischemic stroke (IS), hemorrhagic stroke (HS) and all stroke types combined globally from 1990 to 2013. Methodology: Stroke prevalence, mortality and DALYs were estimated using the Global Burden of Disease 2013 methods. All available data on stroke-related incidence, prevalence, excess mortality and deaths were collected. Statistical models and country-level covariates were employed to produce comprehensive and consistent estimates of prevalence and mortality. Stroke-specific disability weights were used to estimate years lived with disability and DALYs. Means and 95% uncertainty intervals (UIs) were calculated for prevalence, mortality and DALYs. The median of the percent change and 95% UI were determined for the period from 1990 to 2013. Results: In 2013, there were 97,792 (95% UI 90,564-106,016) prevalent cases of childhood IS and 67,621 (95% UI 62,899-72,214) prevalent cases of childhood HS, reflecting an increase of approximately 35% in the absolute numbers of prevalent childhood strokes since 1990. There were 33,069 (95% UI 28,627-38,998) deaths and 2,615,118 (95% UI 2,265,801-3,090,822) DALYs due to childhood stroke in 2013 globally, reflecting an approximately 200% decrease in the absolute numbers of death and DALYs in childhood stroke since 1990. Between 1990 and 2013, there were significant increases in the global prevalence rates of childhood IS, as well as significant decreases in the global death rate and DALYs rate of all strokes in those of age 0-19 years. While prevalence rates for childhood IS and HS decreased significantly in developed countries, a decline was seen only in HS, with no change in prevalence rates of IS, in developing countries. The childhood stroke DALY rates in 2013 were 13.3 (95% UI 10.6-17.1) for IS and 92.7 (95% UI 80.5-109.7) for HS per 100,000. While the prevalence of childhood IS compared to childhood HS was similar globally, the death rate and DALY rate of HS was 6- to 7-fold higher than that of IS. In 2013, the prevalence rate of both childhood IS and HS was significantly higher in developed countries than in developing countries. Conversely, both death and DALY rates for all stroke types were significantly lower in developed countries than in developing countries in 2013. Men showed a trend toward higher childhood stroke death rates (1.5 (1.3-1.8) per 100,000) than women (1.1 (0.9-1.5) per 100,000) and higher childhood stroke DALY rates (120.1 (100.8-143.4) per 100,000) than women (90.9 (74.6-122.4) per 100,000) globally in 2013. Conclusions: Globally, between 1990 and 2013, there was a significant increase in the absolute number of prevalent childhood strokes, while absolute numbers and rates of both deaths and DALYs declined significantly. The gap in childhood stroke burden between developed and developing countries is closing; however, in 2013, childhood stroke burden in terms of absolute numbers of prevalent strokes, deaths and DALYs remained much higher in developing countries. There is an urgent need to address these disparities with both global and country-level initiatives targeting prevention as well as improved access to acute and chronic stroke care.

Added: Oct 29, 2015
Dubovskii P. V., Dubinnyi M. A., Konshina A. G. et al. Biochemistry. 2017. Vol. 56. No. 34. P. 4468-4477.

Today, recombinant proteins are quite widely used in biomedical and biotechnological applications. At the same time, the question about their full equivalence to the native analogues remains unanswered. To gain additional insight into this problem, intimate atomistic details of a relatively simple protein, small and structurally rigid recombinant cardiotoxin I (CTI) from cobra Naja oxiana venom, were characterized using nuclear magnetic resonance (NMR) spectroscopy and atomistic molecular dynamics (MD) simulations in water. Compared to the natural protein, it contains an additional Met residue at the N-terminus. In this work, the NMR-derived spatial structure of uniformly 13C- and 15N-labeled CTI and its dynamic behavior were investigated and subjected to comparative analysis with the corresponding data for the native toxin. The differences were found in dihedral angles of only a single residue, adjacent to the N-terminal methionine. Microsecond-long MD traces of the toxins reveal an increased flexibility in the residues spatially close to the N-Met. As the detected structural and dynamic changes of the two CTI models do not result in substantial differences in their cytotoxicities, we assume that the recombinant protein can be used for many purposes as a reasonable surrogate of the native one. In addition, we discuss general features of the spatial organization of cytotoxins, implied by the results of the current combined NMR and MD study.

Added: Nov 13, 2017
Bocharov E., Lesovoy D., Bocharova O. et al. Biochimica et Biophysica Acta - General Subjects. 2018. Vol. 1862. No. 6. P. 1410-1420.

Background: Prior studies of the human growth hormone receptor (GHR) revealed a distinct role of spatial rearrangements of its dimeric transmembrane domain in signal transduction across membrane. Detailed structural information obtained in the present study allowed elucidating the bases of such rearrangement and provided novel insights into receptor functioning.

Methods: We investigated the dimerization of recombinant TMD fragment GHR254-294 by means of high-resolution NMR in DPC micelles and molecular dynamics in explicit POPC membrane.

Results: We resolved two distinct dimeric structures of GHR TMD coexisting in membrane-mimicking micellar environment and providing left- and right-handed helix-helix association via different dimerization motifs. Based on the available mutagenesis data, the conformations correspond to the dormant and active receptor states and are distinguished by cis-trans isomerization of Phe-Pro266 bond in the transmembrane helix entry. Molecular dynamic relaxations of the structures in lipid bilayer revealed the role of the proline residue in functionally significant rearrangements of the adjacent juxtamembrane region supporting alternation between protein-protein and protein-lipid interactions of this region that can be triggered by ligand binding. Also, the importance of juxtamembrane S-S bonding for signal persistency, and somewhat unusual aspects of transmembrane region interaction with water molecules were demonstrated.

Conclusions: Two alternative dimeric structures of GHR TMD attributed to dormant and active receptor states interchange via allosteric rearrangements of transmembrane helices and extracellular juxtamembrane regions that support coordination between protein-protein and protein-lipid interactions.

General Significance: This study provides a holistic vision of GHR signal transduction across the membrane emphasizing the role of protein-lipid interactions.

Added: Apr 5, 2018
Il'icheva I., Khodikov M., Nechipurenko D. et al. BMC Genomics. 2016. Vol. 17. No. 1. P. 973.


The general structure and action of all eukaryotic and archaeal RNA polymerases machinery have an astonishing similarity despite the diversity of core promoter sequences in different species. The goal of our work is to find common characteristics of DNA region that define it as a promoter for the RNA polymerase II (Pol II).


The profiles of a large number of physical and structural characteristics, averaged over representative sets of the Pol II minimal core promoters of the evolutionary divergent species from animals, plants and unicellular fungi were analysed. In addition to the characteristics defined at the base-pair steps, we, for the first time, use profiles of the ultrasonic cleavage and DNase I cleavage indexes, informative for internal properties of each complementary strand.


DNA of the core promoters of metazoans and Schizosaccharomyces pombe has similar structural organization. Its mechanical and 3D structural characteristics have singular properties at the positions of TATA-box. The minor groove is broadened and conformational motion is decreased in that region. Special characteristics of conformational behavior are revealed in metazoans at the region, which connects the end of TATA-box and the transcription start site (TSS). The intensities of conformational motions in the complementary strands are periodically changed in opposite phases. They are noticeable, best of all, in mammals. Such conformational features are lacking in the core promoters of S. pombe. The profiles of Saccharomyces cerevisiae core promoters significantly differ: their singular region is shifted down thus pointing to the uniqueness of their structural organization. Obtained results may be useful in genetic engineering for artificial modulation of the promoter strength.


Added: Mar 8, 2017
Lyukmanova E., Shenkarev Z., Shulepko M. et al. Journal of biological chemistry. 2015. Vol. 290. P. 23616-23630.

Weak toxin from Naja kaouthia (WTX) belongs to the group of nonconventional “three-finger” snake neurotoxins. It irreversibly inhibits nicotinic acetylcholine receptors and allosterically interacts with muscarinic acetylcholine receptors (mAChRs). Using site-directed mutagenesis, NMR spectroscopy, and computer modeling, we investigated the recombinant mutant WTX analogue (rWTX) which, compared with the native toxin, has an additional N-terminal methionine residue. In comparison with the wild-type toxin, rWTX demonstrated an altered pharmacological profile, decreased binding of orthosteric antagonist N-methylscopolamine to human M1- and M2-mAChRs, and increased antagonist binding to M3-mAChR. Positively charged arginine residues located in the flexible loop II were found to be crucial for rWTX interactions with all types of mAChR. Computer modeling suggested that the rWTX loop II protrudes to the M1-mAChR allosteric ligand-binding site blocking the entrance to the orthosteric site. In contrast, toxin interacts with M3-mAChR by loop II without penetration into the allosteric site. Data obtained provide new structural insight into the target-specific allosteric regulation of mAChRs by “three-finger” snake neurotoxins.

Added: Mar 14, 2017
Riabenko E.A., Tonevitsky E., Tonevitsky A. et al. American Journal of Biomedical Sciences. 2011. Vol. 3. No. 2. P. 90-94.

We studied structural peculiarities of 123 human genes which were previously identified as genes of early response to exercise stress. Compared to protein-coding genes in general, their structure revealed some peculiarities: they are shorter in both coding and non-coding regions and contain fewer introns. This result is in good agreement with the similar results reported for stress-responding genes in other species (yeasts, thale cress, and mice).

Added: Oct 14, 2016
Pouvreau M., Greathouse J. A., Cygan R. T. et al. The Journal of Physical Chemistry C. 2019. Vol. 123. P. 11628-11638.

Toward the development of classical force fields for the accurate modeling of clay mineral-water systems, we have extended the use of metal–O–H (M–O–H) angle bending terms to describe surface Si–O–H bending for hydrated kaolinite edge structures. Kaolinite, comprising linked octahedral Al and tetrahedral Si sheets, provides a rigorous test by combining aluminol and silanol groups with water molecules in hydrated edge structures. Periodic density functional theory and classical force fields were used with molecular dynamics to evaluate the structure, dynamics, hydrogen bonding, and power spectra for deriving optimum bending force constants and optimal equilibrium angles. Cleavage energies derived from density functional theory molecular dynamics calculations indicate the relative stabilities of both AC1 and AC2 edge terminations of kaolinite where Si–OH and Al–(OH2) or Si–OH, Al–OH, and Al–(OH2) groups exist, respectively. Although not examined in this study, the new Si–O–H angle bending parameter should allow for improved modeling of hydroxylated surfaces of silica minerals such as quartz and cristobalite, as well as amorphous silica-based surfaces and potentially those of other silicate and aluminosilicate phases.

Added: Nov 2, 2019