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1.
In the present paper we demonstrate the use of inverse Broyden’s algorithm (IBA) in the simulation of fracture in single iron
crystals. The iron crystal structure is treated as a truss system, while the forces between the atoms situated at the nodes
are defined by modified Morse inter-atomic potentials. The evolution of lattice structure is interpreted as a sequence of
equilibrium states corresponding to the history of applied load/deformation, where each equilibrium state is found using an
iterative procedure based on IBA. The results presented demonstrate the success of applying the IBA technique for modeling
the mechanisms of elastic, plastic and fracture behavior of single iron crystals. 相似文献
2.
A statistical analysis of strong and weak hydrogen bonds in the minor groove of DNA was carried out for a set of 70 drug-DNA
complexes. The terms ‘strong’ and ‘weak’ pertain to the inherent strengths and weakness of the donor and acceptor fragments
rather than to any energy considerations. The dataset was extracted from the protein data bank (PDB). The analysis was performed
with an in-house software, hydrogen bond analysis tool (HBAT). In addition to strong hydrogen bonds such as O—H⋯O and N—H⋯O,
the ubiquitous presence of weak hydrogen bonds such as C—H⋯O is implicated in molecular recognition. On an average, there
are 1.4 weak hydrogen bonds for every strong hydrogen bond. For both categories of interaction, the N(3) of purine and the
O(2) of pyrimidine are favoured acceptors. Donor multifurcation is common with the donors generally present in the drug molecules,
and shared by hydrogen bond acceptors in the minor groove. Bifurcation and trifurcation are most commonly observed. The metrics
for strong hydrogen bonds are consistent with established trends. The geometries are variable for weak hydrogen bonds. A database
of recognition geometries for 26 literature amidinium-based inhibitors of Human African Trypanosomes (HAT) was generated with
a docking study using seven inhibitors which occur in published crystal structures included in the list of 70 complexes mentioned
above, and 19 inhibitors for which the drug-DNA complex crystal structures are unknown. The virtual geometries so generated
correlate well with published activities for these 26 inhibitors, justifying our assumption that strong and weak hydrogen
bonds are optimized in the active site. 相似文献
3.
The contribution of hydrogen bonds to protein-solvent interactions and their impact on structural flexibility and dynamics
of myoglobin are discussed. The shift of vibrational peak frequencies with the temperature of myoglobin in sucrose/water and
glycerol/water solutions is used to probe the expansion of the hydrogen bond network. We observe a characteristic change in
the temperature slope of the O–H stretching frequency at the glass transition which correlates with the discontinuity of the
thermal expansion coefficient. The temperature-difference spectra of the amide bands show the same tendency, indicating that
stronger hydrogen bonding in the bulk affects the main-chain solvent interactions in parallel. However, the hydrogen bond
strength decreases relative to the bulk solvent with increasing cosolvent concentration near the protein surface, which suggests
preferential hydration. Weaker and/or fewer hydrogen bonds are observed at low degrees of hydration. The central O–H stretching
frequency of protein hydration water is red-shifted by 40 cm–1 relative to the bulk. The shift increases towards lower temperatures, consistent with contraction and increasing strength
of the protein-water bonds. The temperature slope shows a discontinuity near 180 K. The contraction of the network has reached
a critical limit which leads to frozen-in structures. This effect may represent the molecular mechanism underlying the dynamic
transition observed for the mean square displacements of the protein atoms and the heme iron of myoglobin.
Received: 10 July 1996 / Accepted: 10 April 1997 相似文献
4.
Russell MJ 《Acta biotheoretica》2007,55(2):133-179
The Earth agglomerates and heats. Convection cells within the planetary interior expedite the cooling process. Volcanoes evolve
steam, carbon dioxide, sulfur dioxide and pyrophosphate. An acidulous Hadean ocean condenses from the carbon dioxide atmosphere.
Dusts and stratospheric sulfurous smogs absorb a proportion of the Sun’s rays. The cooled ocean leaks into the stressed crust
and also convects. High temperature acid springs, coupled to magmatic plumes and spreading centers, emit iron, manganese,
zinc, cobalt and nickel ions to the ocean. Away from the spreading centers cooler alkaline spring waters emanate from the
ocean floor. These bear hydrogen, formate, ammonia, hydrosulfide and minor methane thiol. The thermal potential begins to
be dissipated but the chemical potential is dammed. The exhaling alkaline solutions are frustrated in their further attempt
to mix thoroughly with their oceanic source by the spontaneous precipitation of biomorphic barriers of colloidal iron compounds
and other minerals. It is here we surmise that organic molecules are synthesized, filtered, concentrated and adsorbed, while
acetate and methane—separate products of the precursor to the reductive acetyl-coenzyme-A pathway—are exhaled as waste. Reactions
in mineral compartments produce acetate, amino acids, and the components of nucleosides. Short peptides, condensed from the
simple amino acids, sequester ‘ready-made’ iron sulfide clusters to form protoferredoxins, and also bind phosphates. Nucleotides
are assembled from amino acids, simple phosphates carbon dioxide and ribose phosphate upon nanocrystalline mineral surfaces.
The side chains of particular amino acids register to fitting nucleotide triplet clefts. Keyed in, the amino acids are polymerized,
through acid–base catalysis, to alpha chains. Peptides, the tenuous outer-most filaments of the nanocrysts, continually peel
away from bound RNA. The polymers are concentrated at cooler regions of the mineral compartments through thermophoresis. RNA
is reproduced through a convective polymerase chain reaction operating between 40 and 100°C. The coded peptides produce true
ferredoxins, the ubiquitous proteins with the longest evolutionary pedigree. They take over the role of catalyst and electron
transfer agent from the iron sulfides. Other iron–nickel sulfide clusters, sequestered now by cysteine residues as CO-dehydrogenase
and acetyl-coenzyme-A synthase, promote further chemosynthesis and support the hatchery—the electrochemical reactor—from which
they sprang. Reactions and interactions fall into step as further pathways are negotiated. This hydrothermal circuitry offers
a continuous supply of material and chemical energy, as well as electricity and proticity at a potential appropriate for the
onset of life in the dark, a rapidly emerging kinetic structure born to persist, evolve and generate entropy while the sun
shines.
An erratum to this article can be found at 相似文献
5.
Boaz G. Oliveira Maria C. A. Lima Ivan R. Pitta Suely L. Galdino Marcelo Z. Hernandes 《Journal of molecular modeling》2010,16(1):119-127
A theoretical study is presented with the aim to investigate the molecular properties of intermolecular complexes formed by
the monomeric units of polyvinylpyrrolidone (PVP) or polyethyleneglycol (PEG) polymers and a set of four imidazolidine (hydantoine)
derivatives. The substitution of the carbonyl groups for thiocarbonyl in the hydantoin scaffold was taken into account when
analyzing the effect of the hydrogen bonds on imidazolidine derivatives. B3LYP/6-31G(d,p) calculations and topological integrations
derived from the quantum theory of atoms in molecules (QTAIM) were applied with the purpose of examining the N–H⋯O hydrogen
bond strengths formed between the amide group of the hydantoine ring and the oxygen atoms of PVP and PEG polymers. The effects
caused by the N–H⋯O interaction fit the typical evidence for hydrogen bonds, which includes a variation in the stretch frequencies
of the N–H bonds. These frequencies were identified as being vibrational red-shifts because their values decreased. Although
the values of such calculated interaction energies are between 12 and 33 kJ mol−1, secondary intermolecular interactions were also identified. One of these secondary interactions is formed through the interaction
of the benzyl hydrogen atoms with the oxygen atoms of the PVP and PEG structures. As such, we have analyzed the stretch frequencies
on the C–H bonds of the benzyl groups, and blue-shifts were identified on these bonds. In this sense, the intermolecular systems
formed by hydantoine derivatives and PVP/PEG monomers were characterized as a mix of red-shifting and blue-shifting hydrogen-bonded
complexes. 相似文献
6.
The reduction–oxidation (redox) state of peatland pore waters plays an important role in many peatland biogeochemical processes.
Recent research has also shown that the interface between ecosystems, or the ecotone, may be responsible for a disproportionate
amount of biogeochemical activity when material and/or energy is hydrologically transported between ecosystems. The purpose
of this research was to examine the spatiotemporal dynamics of redox conditions across two geomorphically distinct Boreal
Precambrian Shield upland–peatland ecotones to determine the spatial and temporal scales at which these ecotones may be important.
Pore water chemistry of iron and sulphur species was monitored across two upland–peatland ecotones in northwestern Ontario
in conjunction with hydrological measurements under both stormflow and nonstormflow conditions. In addition, one upland–peatland
ecotone was instrumented to make continuous measurements of in situ redox potential (Eh) over a 12-day period to determine whether measurements at a high temporal scale could provide additional
insights into the transfer of nutrients across the upland–peatland interface. Results indicated that hydrology—specifically,
groundwater flowpath and the strength of the hydrological connection between upland and peatland—determined the spatial extent
of the ecotone as a biogeochemical hotspot. In situ Eh measurements showed that these ecotones may be most important over
a scale of only several hours and are largely affected by lateral hydrological flows from the upland. The role of both hot
spots and hot moments in biogeochemistry must be considered to accurately estimate the ability of a single ecosystem to process
chemical inputs. 相似文献
7.
Hannan MA Faraji B Tanguma J Longoria N Rodriguez RC 《Biological trace element research》2009,127(1):6-15
The dietary intake of zinc (Zn), iron (Fe), selenium (Se), and iodine (I) of 31 lactating Mexican–American women attending
the Hidalgo County WIC program in Rio Grande Valley (RGV), Texas was estimated from 24-h dietary recall interviews. Milk samples
were obtained from lactating mothers who had infants 3 months of age and younger. Milk samples were collected in two visits
to assess change in breast milk composition after 1–3 months postpartum: group A—after 30–45 days and group B—75–90 days.
Dietary intakes indicated that the study participants had significantly inadequate percent energy intakes than the DRI (Dietary
Recommended Intakes) percent recommended kilocalorie values but protein intakes were substantially higher than the percent
recommended values. The estimated percent Zn, Fe, Se, and I intakes were also significantly lower than the DRI percent recommended
values. The lactating mothers consumed significantly less Zn, Se, and I when compared to the Recommended Dietary Allowances
(RDA) even though Fe intake was higher than the RDA value. Breast milk concentration of Zn, Fe, and Se were in agreement within
the range of representative values for Constituents of Human Milk but I has significantly less concentration than the representative
value. There was no statistically significant correlation observed between dietary intake and milk concentration of Zn, Fe,
Se, and I. This study compares the estimated dietary intake of zinc, iron, selenium, and iodine to the concentration of these
trace elements in the maternal milk of lactating women of Mexican–American heritage who attend the Rio Grande Valley WIC clinic. 相似文献
8.
We recently showed in an animal model that iron isotopic composition varies substantially between different organs. For instance,
iron in ferritin-rich organs—such as the major storage tissues liver, spleen, and bone marrow—contain a larger fraction of
the heavy iron isotopes compared with other tissues, including blood. As a consequence, partitioning of body iron into red
blood cells and storage compartments should be reflected in the isotopic pattern of blood iron. To confirm this hypothesis,
we monitored blood iron isotope patterns in iron-overloaded subjects undergoing phlebotomy treatment by multicollector inductively
coupled plasma mass spectrometry. We found that bloodletting and consequential replacement of lost blood iron by storage iron
led to a substantial increase of the heavy isotope fraction in the blood. The progress of iron depletion therapy and blood
loss was quantitatively traceable by isotopic shifts of as much as +1‰ in δ(56Fe). These results show that—together with iron absorption efficiency—partitioning of iron between blood and iron storage
tissues is an important determinant of blood iron isotopic patterns, which could make blood iron isotopic composition the
first composite measure of iron metabolism in humans. 相似文献
9.
We have identified a new class of microtubule-binding compounds—noscapinoids—that alter microtubule dynamics at stoichiometric
concentrations without affecting tubulin polymer mass. Noscapinoids show great promise as chemotherapeutic agents for the
treatment of human cancers. To investigate the structural determinants of noscapinoids responsible for anti-cancer activity,
we tested 36 structurally diverse noscapinoids in human acute lymphoblastic leukemia cells (CEM). The IC50 values of these noscapinoids vary from 1.2 to 56.0 μM. Pharmacophore models of anti-cancer activity were generated that identify
two hydrogen bond acceptors, two aromatic rings, two hydrophobic groups, and one positively charged group as essential structural
features. Additionally, an atom-based quantitative structure–activity relationship (QSAR) model was developed that gave a
statistically satisfying result (R
2 = 0.912, Q
2 = 0.908, Pearson R = 0.951) and effectively predicts the anti-cancer activity of training and test set compounds. The pharmacophore model presented
here is well supported by electronic property analysis using density functional theory at B3LYP/3-21*G level. Molecular electrostatic
potential, particularly localization of negative potential near oxygen atoms of the dimethoxy isobenzofuranone ring of active
compounds, matched the hydrogen bond acceptor feature of the generated pharmacophore. Our results further reveal that all
active compounds have smaller lowest unoccupied molecular orbital (LUMO) energies concentrated over the dimethoxy isobenzofuranone
ring, azido group, and nitro group, which is indicative of the electron acceptor capacity of the compounds. Results obtained
from this study will be useful in the efficient design and development of more active noscapinoids. 相似文献
10.
Abstrac The processes of dissociation and recombination of CO molecules in the plasmas of discharges in He/CO and He/CO/Xe mixtures
under conditions characteristic of sealed-off CO lasers are investigated. The concentrations of CO molecules and the main
products of their dissociation—O and C atoms and CO2 molecules—are measured simultaneously for the first time, and the time evolution of the initial working mixture composition
in the discharge is calculated. It is shown that the main channel for the regeneration of CO molecules in a sealed-off discharge
is the heterogeneous recombination of C and O atoms. The rate constants for this process are estimated.
__________
Translated from Fizika Plazmy, Vol. 30, No. 9, 2004, pp. 845–854.
Original Russian Text Copyright ? 2004 by Grigorian, Kochetov. 相似文献
11.
Cell-free supernatant from Shewanella oneidensis MR-1 reduced carbon tetrachloride to chloroform, a suspension of Fe(III) and solid Fe(III) to iron (II). The putative reducing
agent was tentatively identified as menaquinone-1 (MQ-1)—a water-soluble menaquinone with a single isoprenoid residue in the
side chain. Synthetic MQ-1 reduced carbon tetrachloride to chloroform and amorphous iron (III) hydroxide to iron (II). To
test the generality of this result among menaquinones, the reductive activities of vitamin K2 (MQ-7)—a lipid-associated menaquinone with 7 or 8 isoprenoid residues—was evaluated. This molecule also reduced carbon tetrachloride
to chloroform and iron (III) to iron (II). The results indicate that molecules within the menaquinone family may contribute
to both the extracellular and cell-associated reduction of carbon tetrachloride and iron (III). 相似文献
12.
Kozina V Geist D Kubinová L Bilić E Karnthaler HP Waitz T Janáček J Chernyavskiy O Krhen I Ježek D 《Histochemistry and cell biology》2011,135(2):215-228
Within the human testis, Reinke’s crystals are found in Leydig cells but their nature and function are poorly understood.
The aim of our study was to investigate the properties of Reinke’s crystals in man with the normal morphology of the testis
(control group) and infertile patients diagnosed with cryptorchidism. 20 biopsies from infertile patients and six biopsies
from men with regular spermatogenesis (20–30 years.) were used. Sections of the testis tissue were stained with haematoxylin
and eosin and a modified Masson’s method. Specimens were observed by bright field, confocal and transmission electron microscopy
(TEM). The number of Reinke’s crystals in investigated groups was determined applying stereological methods. In both groups,
Reinke’s crystals were noted within the cytoplasm and nuclei of Leydig cells. Some “free” crystals were found within the interstitial
space, outside Leydig cells. Confocal microscopy proved to be very useful in the assessment of the shape and 3D reconstruction
of the crystal. TEM analysis confirmed a hexagonal form of the crystal, while crystallographic data on sections of 70–300 nm
thickness provided a better insight into the organization of the crystal lattice. Stereological analysis revealed a significant
increase in the number of crystals in cryptorchid testes when compared with controls. Increased number of crystals in cryptorchid
specimens leads to the assumption that the prolonged exposure to higher (abdominal) temperature might stimulate enzymes involved
in the synthesis of the proteins of the crystal. However, the exact molecular nature of the crystal lattice remains in both
normal and cryptorchid testis obscure. 相似文献
13.
A coarse-grained model of polypeptide chains confined in a slit formed by two parallel impenetrable surfaces was studied.
The chains were flexible heteropolymers (polypeptides) built of two kinds of united atoms—hydrophobic and hydrophilic. The
positions of the united atoms were restricted to the vertices of a [310] lattice. The force field consisted of a rigorous
excluded volume, a long-distance potential between a pair of amino-acid residues and a local preference for forming secondary
structure (helices). The properties of the chains were studied at a wide range of temperatures from good to bad solvent conditions.
Monte-Carlo simulations were carried out using the algorithm based on the chain’s local changes of conformation and employing
the Replica Exchange technique. The influence of the chain length, the distances between the confining surfaces, the temperature
and the force field on the dimension and the structure of chains were studied. It was shown that the presence of the confinement
chain complicates the process of the chain collapse to low-temperature structures. For some conditions, one can find a rapid
decrease of chain size and a second transition indicated by the rapid decrease of the total energy of the system.
Figure A scheme of a polypeptide chain built on a [310] lattice and confined to a slit formed by a pair of parallel impenetrable
surfaces
Proceedings of “Modeling Interactions in Biomolecules II,” Prague, September 5th–9th, 2005. 相似文献
14.
A Review of the Antioxidant Mechanisms of Polyphenol Compounds Related to Iron Binding 总被引:2,自引:0,他引:2
In this review, primary attention is given to the antioxidant (and prooxidant) activity of polyphenols arising from their
interactions with iron both in vitro and in vivo. In addition, an overview of oxidative stress and the Fenton reaction is
provided, as well as a discussion of the chemistry of iron binding by catecholate, gallate, and semiquinone ligands along
with their stability constants, UV–vis spectra, stoichiometries in solution as a function of pH, rates of iron oxidation by
O2 upon polyphenol binding, and the published crystal structures for iron–polyphenol complexes. Radical scavenging mechanisms
of polyphenols unrelated to iron binding, their interactions with copper, and the prooxidant activity of iron–polyphenol complexes
are briefly discussed. 相似文献
15.
Density functional theory was utilized to study the electronic properties of boron nitride (BN) sheets, taking into account
the presence of defects. The structure considered consisted of a central hexagon surrounded by alternating pentagons (three)
and heptagons (three). The isocoronene cluster model with an armchair edge was used with three different chemical compositions.
In the first structure, three B–B bonds were formed where one B in the dimer was part of the central hexagon. In the second
structure, three N–N–N bonds were formed at the periphery of the cluster, around the central hexagon. In the third structure,
three N–N bonds were formed in a similar fashion to the first model. Our results indicated that the third structure was the
most stable configuration; this exhibited planar geometry, semiconductor behavior, and ionic character. To explore the effects
of doping, we replaced B and N atoms with C atoms, considering different atomic positions in the central hexagon. When an
N atom was replaced with a C atom, the new structure was a semiconductor, but when a B atom was replaced with a C atom, the
new structure was a semimetal. At the same time, the polarity increased, inducing covalent behavior. Replacing two N atoms
with two C atoms also resulted in a semiconductor, while replacing two B atoms with two C atoms yielded a semimetal; in both
cases the bonding was covalent. When three B (three N) atoms of the central hexagon were replaced with three C atoms, the
new structure exhibited a transition to a conductor (remained a semiconductor) with low polarity. When monovacancies (N) and
divacancies (B and N) were inserted into the lattice, the system was transformed into a covalent semiconductor. Finally, the
electrostatic potential surface was calculated in order to explore intermolecular properties such as the charge distribution,
which showed how the reactivity of the boron nitride sheets was affected by doping and orbital hybridization. 相似文献
16.
The concentration of twelve elements—potassium, calcium, manganese, iron, cobalt, nickel, copper, zinc, arsenic, selenium,
bromine, and rubidium—in anterior pituitaries from human subjects and rats was measured using Particle Induced X-ray Emission
(PIXE). The human material included anterior pituitaries from 37 normal human subjects, 27 males and 10 females, all of whom
died from traumatic lesions. Excluded from the investigations were persons with alcohol abuse, regular use of drugs, and babies
younger than 1 year.
For selenium, zinc, bromine, and to some extent copper, there was good correlation between the amounts found in anterior pituitaries
from rats and human subjects. A significant difference between male and female rat pituitaries was observed for copper, iron,
and rubidium, whereas for humans significant difference was only observed for manganese. Anterior pituitaries from human females
contained generally more zinc than male glands, but the concentration of zinc in young males was higher than in females. The
present study also indicates age related differences in the copper content in anterior pituitaries from human subjects, since
pituitaries from humans between 15–45 years contained 25% more copper than those from younger or older persons. The opposite
pattern was observed in males. For such elements as Cu, Fe, Mn, and Se, the content in the anterior pituitary from human subjects
was 1.6–2 times that stated for other endocrine organs. 相似文献
17.
The development of Gryllus argentinus Sauss. was studied under stable laboratory conditions: the temperature of 26°C, the air humidity of 60%, and the photoperiod
of 12h light: 12 h dark. The life cycle of Gryllus argentinus includes four stages: egg, pronymph, nymph, and adult. The duration of embryonic development is 18 days. The depth of egg
bedding in the peat is 9.63 ± 0.12 mm (n =145), the clutch containing 2–4 eggs. A female can lay over 1100 viable eggs during the entire oviposition period. Nymphal
development includes 9 instars and lasts 97 days. The duration of nymphal instars (days) is: I—5; II—6; III—6; IV—6; V—8;
VI—10; VII—13; VIII—14; IX—29. The duration of the adult life is 51 days in males and 69 days, in females. In the imaginal
ontogenesis of males and females, three periods can be distinguished: pre-reproductive, reproductive, and postreproductive.
Males start to emit the aggressive signal on the 6th (5–8th) day (the pre-reproductive period). They enter the reproductive
period (start to emit the calling song) on the 9th (8–13th) day. Females enter the reproductive period (become capable of
responding to the calling song and of copulation) on the 9th (8–10th) day. Oviposition starts on the day after the first copulation.
The reproductive period lasts about 40 (15–59) days in males and 58 (21–70) days in females. The post-reproductive period
starts in females at the moment of finishing the egg laying period and in males, with disappearance of reproductive behavior.
The period ends in the animal’s death. 相似文献
18.
Choi JH Niketić SR Djordjević I Clegg W Harrington RW 《Journal of molecular modeling》2012,18(5):2135-2146
The crystal structure of [Cr(edda)(acac)] (edda = ethylediamine-N,N′-diacetate; acac = acetylacetonato) has been determined
by a single crystal X-ray diffraction study at 150 K. The chromium ion is in a distorted octahedral environment coordinated
by two N and two O atoms of chelating edda and two O atoms of acac, resulting in s-cis configuration. The complex crystallizes in the space group P21/c of the monoclinic system in a cell of dimensions a = 10.2588(9), b = 15.801(3), c = 8.7015(11) ?, β =101.201(9)° and Z = 4.
The mean Cr-N(edda), Cr-O(edda) and Cr-O(acac) bond distances are 2.0829(14), 1.9678(11) and 1.9477(11) ? while the angles
O-Cr-O of edda and O-Cr-O of acac are 171.47(5) and 92.72(5)°, respectively. The crystal structure is stabilized by N–H⋯O
hydrogen bonds linking [Cr(edda)(acac)] molecules in distinct linear strands. The visible electronic and IR spectroscopic
properties are also discussed. An improved, physically more realistic force field, Vibrationally Optimized Force Field (VOFF),
capable of reproducing structural and vibrational properties of [Cr(edda)(acac)] was developed and its transferability demonstrated
on selected chromium(III) complexes with similar ligands. 相似文献
19.
V. N. Davydova V. P. Nagorskaya V. I. Gorbach A. A. Kalitnik A. V. Reunov T. F. Solov’eva I. M. Ermak 《Applied Biochemistry and Microbiology》2011,47(1):103-108
Enzymatic (the action of lysozyme) and chemical (the action of hydrogen peroxide) hydrolysis of chitosans with various degree
of acetylation (DA)—25, 17, and 1.5%—was performed. Purification and fractioning of the hydrolysis products were performed
using dialysis, ultrafiltration, and gel-penetrating chromatography. Low-molecular (LM) derivatives of the polysaccharide
with molecular masses from 17 to 2 kDa were obtained. The study of their antiviral activity against the tobacco mosaic virus
(TMV) showed that these samples inhibited the formation of local necroses induced by the virus for 50–90%. The antiviral activity
of the LM chitosans significantly increased with the lowering of their polymerization degree. Furthermore, the products of
the enzymatic hydrolysis possessed lower activity than the chitosan samples obtained as a result of chemical hydrolysis. It
was revealed that the exhibition of the antiviral activity weakly depended on the degree of acetylation of the samples. 相似文献
20.
Joshy P. Yesudas Fareed Bhasha Sayyed Cherumuttathu H. Suresh 《Journal of molecular modeling》2011,17(2):401-413
A hydrogen bond prediction tool HBPredicT is developed for detecting structural water molecules and CH···π interactions in
PDB files of protein-ligand complexes. The program adds the missing hydrogen atoms to the protein, ligands, and oxygen atoms
of water molecules and subsequently all the hydrogen bonds in the complex are located using specific geometrical criteria.
Hydrogen bonds are classified into various types based on (i) donor and acceptor atoms, and interactions such as (ii) protein-protein,
(iii) protein-ligand, (iv) protein-water, (v) ligand-water, (vi) water-water, and (vii) protein-water-ligand. Using the information
in category (vii), the water molecules which form hydrogen bonds with the ligand and the protein simultaneously–the structural
water–is identified and retrieved along with the associated ligand and protein residues. For CH···π interactions, the relevant
portions of the corresponding structures are also extracted in the output. The application potential of this program is tested
using 19 HIV-1 protease and 11 PTP1B inhibitor complexes. All the systems showed presence of structural water molecules and
in several cases, the CH···π interaction between ligand and protein are detected. A rare occurrence of CH···π interactions
emanating from both faces of a phenyl ring of the inhibitor is identified in HIV-1 protease 1D4L. 相似文献