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1.
Monika Tarnowska Adam Liwo Mark D. Shenderovich Inta Liepiņa Alexander A. Golbraikh Zbigniew Grzonka Anna Tempczyk 《Journal of computer-aided molecular design》1993,7(6):699-719
Summary The effect of the substitution in position 1 on the low-energy conformations of the oxytocin/vasopressin 20-membered ring was investigated by means of molecular mechanics. Three representative substitutions were considered: -mercapto-,-dimethyl)propionic acid (Dmp), (-mercapto-,-cyclopentamethylene)propionic acid (Cpp), both forming strong antagonists, and (,-dimethyl--mercapto)propionic acid (-Dmp), forming analogs of strongly reduced biological activity, with the -mercaptopropionic (Mpa) residue taken as reference. Both ECEPP/2 (rigid valence geometry) and AMBER (flexible valence geometry) force fields were employed in the calculations. Three basic types of backbone conformations were taken into account which are distinguished by the type of -turn at residues 3 and 4: 1/III, II, and I/III, all types containing one or two intra-annular hydrogen bonds. The allowed (ring-closed) disulfide-bridge conformations were searched by an algorithm formulated in terms of scanning the disulfide-bridge torsional angle C-S-S-C. The ECEPP/2 and AMBER energies of the obtained conformations were found to be in reasonable agreement. Two of the low-energy conformers of the [Mpa1]-compound agreed very well with the cyclic part of the two conformers found in the crystal structure of [Mpa1]-oxytocin. An analysis of the effect of -substitution on relative energies showed that the conformations with the N-C-CH2-CH2 (1) and C-CH2-CH2-S (1) angles of the first residue around (–100°, 60°) and (100°, –60°) are not affected; this in most cases implies a left-handed disulfide bridge. In the case of -substitution the allowed values of 1 are close to ± 60°. This requirement, being in contradiction to the one concerning -substitution, could explain the very low biological activity of the -substituted analogs. The conformational preferences of substituted compounds can largely be explained by the analysis of local interactions within the first residue. Based on the selection of the conformations which are low in energy for both the reference and -substituted compounds, two distinct types of possible binding conformations were proposed, the first one being similar to the crystal conformer with a left-handed disulfide bridge, the second one having a right-handed bridge, but a geometry different from that of the crystal conformer with the right-handed bridge. The first type of disulfide-bridge arrangement is equally favorable for both I/III and II types of backbone structure, while the second one is allowed only for the II type of backbone. No conformation of the I/III type has a low enough energy to be considered as a possible binding conformation for all of the active compounds studied in this work. 相似文献
2.
Water‐in‐oil (w/o) emulsions were prepared with phosphatidylcholine‐depleted lecithin or polyglycerol polyricinoleate (PGPR) as emulsifying agents. The effect of different laboratory emulsification devices and the effect of sodium chloride on particle size distribution, coalescence stability, and water droplet sedimentation were investigated. The properties of lecithin‐stabilized w/o emulsions were found to depend more strongly on the emulsifying method than those prepared with PGPR. The rotor‐stator system was not suitable for preparing stable w/o emulsions with lecithin. Whereas the addition of salt was essential to achieve coalescence‐stable emulsions prepared with PGPR, the presence of NaCl favored the coalescence of water droplets and phase separation in emulsions containing lecithin. 相似文献
3.
Kalnina I Klimkane L Kirilova E Toma MM Kizane G Meirovics I 《Journal of fluorescence》2007,17(6):619-625
The fluorescent probe-aminoderivative of benzanthrone, ABM (developed at Riga Technical University, Riga, Latvia) was used
to characterize the membranes of lymphocytes of cancer patients: 46 patients with gastrointestinal diseases, 13 patients having
different primary localizations with massive metastases and intoxication. Patients were divided into three groups: (1) with
decreased fluorescence intensity, (2) normal fluorescence intensity, (3) increased fluorescence intensity. The lymphocytes
distribution among subsets differed between groups, in correspondence to the level of florescence intensity. Surgical treatment
affected the main immunological parameters and elevated the functional activity of lymphocytes. In the advanced tumors group,
fluorescence intensity correlates with the survival rate. Results suggest that determination of lymphocytes functional activity
by ABM can aid evaluation of the immune status in cancer patients. 相似文献
4.
Elena M. Kirilova Inta Kalnina Tija Zvagule Natalija Gabruseva Natalja Kurjane Irina I. Solomenikova 《Journal of fluorescence》2011,21(3):923-927
The use of hydrophobic fluorescent probe ABM (benzanthrone derivative) and albumin autofluorescence allowed show conformational
alterations in Chernobyl clean-up workers blood plasma. Results obtained in 1996–1997 suggest that acidic expansion of plasma
albumin takes place. Latest data (2006–2008) result in splitting of albumin alterations onto two stages - acidic expansion
and N-F transition. The N-F transition is accompanied by the blue shift of fluorescence spectra and dehydration of tryptophanyl
region of albumin molecule. In 2007 obtained.patterns of ABM spectra had never been previously seen in examined healthy individuals
or patients with tuberculosis, multiple sclerosis, rheumatoid arthritis, etc. Patterns of ABM fluorescence spectra are associated
with conformational changes of blood plasma albumin. The use of probe ABM and albumin auto-fluorescence allowed show conformational
alterations in albumin of Chernobyl clean-up workers blood plasma. It is necessary to note that all investigated parameters
significantly differ in observed groups of patients. These findings reinforce our understanding that the blood plasma albumin
is a significant biological target of radiation. It may be concluded that fluorescence characteristics are representative
of radiation induced albumin alterations and its carrier function. 相似文献
5.
Inta Kalnina Ruta Bruvere Tija Zvagule Natalija Gabruseva Laura Klimkane Elena Kirilova Imants Meirovics Gunta Kizane 《Journal of fluorescence》2010,20(1):9-17
The fluorescent probe ABM (3-aminobenzanthrone derivative) one of the fluorescent probes synthesized in Riga Technical University
proved to be an excellent, independent model for studying cell membranes. In our work we have investigated the possibility
of using the fluorescent probe ABM for detection of immune state in patients with different pathologies. There is a strong
correlation among all studied ABM spectral parameters, immunological characteristics, clinical and laboratory investigations
of the all observed patients groups. The obtained results suggest that ABM spectral parameters in cell suspension reflect
the alterations of the cellular mechanisms of immunity. Therefore fluorescent method could be used as preliminary screening
test in immune diagnostics instead of more expensive, time consuming methods (subset detection, radioisotope method etc.)
used as routine in clinics. Spectral parameters of ABM reflect a wide range of interrelated (interdependent) characteristics
of cells (physico-chemical state and microviscosity of membrane, proliferating and lipid metabolic activity of cells, distribution
of cells among subsets). The observed change of the studied parameters reflects alterations of the cellular mechanisms of
immunity which is a main focus for its application as preliminary screening test in immune diagnostics. The fluorescence based
method is sensitive, less expensive and time consuming, technically simple and convenient. 相似文献
6.
Sopit Phetsang Jukreera Panyakaew Sunanta Wangkarn Nopakarn Chandet Angkhana Inta Sila Kittiwachana 《Natural product research》2019,33(4):553-556
Essential oils from the aerial parts of four Elsholtzia species; Elsholtzia stachyodes, Elsholtzia communis, Elsholtzia griffithii and Elsholtzia beddomei were obtained by steam distillation and their chemical components were analysed by gas chromatography-mass spectrometry (GC-MS). Principle Component Analysis was used to identify the chemical variations in the essential oils from these plants, which could be categorised into two groups according to their main chemical components which are acylfuran derivatives and oxygenated monoterpenes. Additionally, the anti-acne inducing bacterial activity against Staphylococcus aureus and Staphylococcus epidermidis were evaluated. The oil from E. stachyodes was the most efficacious against the growth of S. aureus and S. epidermidis having MIC values of 0.78 and 1.56 μL/mL, respectively, and exhibited five times more effective than erythromycin (standard antibiotic). 相似文献
7.
8.
Inta Liepina Paul A. Janmey Cezary Czaplewski Adam Liwo 《Journal of Molecular Structure》2003,630(1-3):309-313
Gelsolin is an actin-severing protein whose action is promoted by Ca2+ ions and inhibited by binding to lipid phosphoinositides incorporated in the inner leaflet of the plasma membrane inner lipid bilayer. In this study, we carried out molecular dynamics (MD) simulations to investigate the influence of calcium cations on the conformation of gelsolin S2 domain. First, gelsolin S2 domain taken from the crystal structure of apo-gelsolin (PDB code: 1D0N) was subjected to three 1100 ps MD simulations in a periodic water box with the
5.0 force field at T=298 K. In the first simulation (S2_Ca2+) excess concentration of Ca2+ was applied, in the second one (S2_phys) the concentration of Ca2+ ions was physiological and in the third one (S2_w) no Ca2+ ions were added. The results of MD simulations showed high conformational flexibility of the N-terminal part of the S2 domain. S2_w deviated from the starting structure considerably more that S2_phys and S2_Ca2+ suggesting that Ca2+ ions stabilize the conformation of the S2 domain of gelsolin. 相似文献
9.
Fluorescent properties of two naphthalimides and a phenalenone derivative in organic solvents and when they bind to human
peripheral blood lymphocytes were investigated. Different spectral characteristics were observed using lymphocytes of healthy
donors and patients with nonmalignant (chronic myeloid leukemia) and malignant (B-cell lymphoid leukemia) diseases. It was
found that spectral properties of the used fluorophores in cell suspension qualitatively characterize its structural and functional
alterations during pathological phenomena. The intensity of fluorescence increased in samples from patients with B-cell lymphoid
leukemia, and the fluorescence maximum shifted to the long-wavelength region by 20 nm compared with normal lymphocytes. It
is concluded that 3-isopropyloxy-6-morpholino-2-phenylphenalen-1-one as most promising probe may be applied to the study of
malignant diseases. 相似文献
10.
Inta Scherze Karin Marzilger Gerald Muschiolik 《Colloids and surfaces. B, Biointerfaces》1999,12(3-6):213-221
To investigate the emulsifying properties and adsorption behaviour of high molecular amphiphilic substances such as proteins, it is important to maintain the native status of the used samples. The new method of micro porous glass (MPG) emulsification could offer an opportunity to do this because of the low shear forces. The oil-in-water emulsions were produced by dispersing the hydrophobic phase (liquid butter fat or sunflower oil) through the MPG of different average pore diameters (dp=0.2 or 0.5 μm) into the flowing continuous phase containing the milk proteins (from reconstituted skim milk and buttermilk). The emulsions were characterised by particle size distribution, creaming behaviour and protein adsorption at the hydrophobic phase. The particle size distribution of protein-stabilised MPG emulsions is determined by the pore size of MPG, the velocity of continuous phase (or wall shear stress σw) and the transmembrane pressure. A high velocity of
=2 m s−1 (σw=13.4 Pa) and low pressure (pressure of disperse phase slightly exceeded the critical pressure ΔpTM=4.5 bar of 0.2 μm-MPG) led to the smallest droplet diameter. As a consequence of average droplet diameters of d43>3.5 μm creaming was observed without centrifugation in all MPG emulsions after 24 h, but no coalescence of the oil droplets occurred. The study of protein adsorption showed that the MPG emulsification at low shear forces resulted in lower protein load values (2.5±0.5 mg m−2) than pressure emulsification (11.5±1.0 mg m−2). In addition, the various emulsification conditions (MPG or pressure homogenization) led to differences in the relative proportions of casein fractions, whey proteins and milk fat globule membranes (MFGM) at the fat globule surfaces. 相似文献