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V Razumas

Publications and source records attributed to V Razumas.

8 recordsLinked to original sources
PubMed2005

Synthesis and aqueous phase behavior of 1-glyceryl monooleyl ether.

Synthesis of 1-glyceryl monooleyl ether (GME) has been accomplished yielding material of high purity (99.6%). The aqueous phase behavior of synthesized lipid has been investigated by using polarized microscopy and small angle X-ray diffraction. As a result, a partial temperature-composition phase diagram has been constructed. GME forms a reversed micellar solution and reversed hexagonal liquid crystalline phase at low and high hydration, respectively. The hexagonal phase coexists with excess water and is stable up to about 63 degrees C. These findings make GME an interesting alternative to glycerol monoesters in various fields of applications.

Fatty Alcohols↗
PubMed2005

Inhibitory effect of N,O-acil-threo-DL-phenylserine derivatives on rat adjuvant arthritis.

Rat adjuvant arthritis (AA), a model of chronic inflammation and an experimental model of rheumatoid arthritis (RA) has been used to evaluate the possible anti-inflammatory action of seventeen N,O-acil-threo-DL-phenylserines 1-17. For this purpose experiments on 200 male Wistar rats were performed. The obtained results showed that oral administration of all compounds, except 15, inhibited the development of AA as compared with the control group. Although the level of arthritic suppression of some preparations was equivalent to aspirin or exceeded it (compounds 2-4, 6, 10, 13), only the preparation 10 in a dose of 100 mg/kg significantly change the paw swelling (P < 0.02) which decreased by 27.9-31.7% at the end of experiment. Pronounced inhibition (P < 0.05-0.01) of joint swelling and the indices of pathological process activity were revealed in earlier stages of AA under the treatment with compounds such as 6 and 11. The antiinflammatory effect of some compounds (9, 11, 13) was observed in the middle of the experiment, although only compound 9 showed significant suppression by 35.9-37.9% at this stage (P < 0.01-0.001) which also markedly decreased ESR (P < 0.05). The latter index was significantly reduced by the action of preparations 2-4, 6-8. Most of the compounds investigated improved blood indices and prevented the development of polyarthritis.

Animals↗
PubMed2004

Anion effect on mediated electron transfer through ferrocene-terminated self-assembled monolayers.

Inorganic anions strongly influence the electron transfer rate from the ascorbate to the ferrocene-terminated self-assembled monolayer (SAM) composed of 9-mercaptononyl-5'-ferrocenylpentanoate (Fc(CH2)4COO(CH2)9SH, MNFcP). At the 1 M concentration level of the supporting anion (sodium salt electrolyte), a more than 10-fold increase in the electrocatalytic oxidation rate constant of the ascorbate is observed in the following sequence: PF6-, ClO4-, BF4-, NO3-, Cl-, SO4(2-), NH2SO3- (sulfamate), and F-. The sequence corresponds to the direction of increasing hydration energy of the corresponding anion, suggesting that highly hydrated ions promote electrocatalytic electron transfer to the ferrocene-terminated SAMs, while poorly hydrated ions inhibit it. Fourier transform surface-enhanced Raman spectroscopy (FT-SERS), in combination with cyclic voltammetry, indicates the formation of surface ion pairs between the ferricinium cation (Fc+) and low hydration energy anions, while, on the contrary, no ion pairs were observed in the electrolytes dominated by the high hydration energy anions. Though it is evident that the ion-pairing ability of hydrophobic anions is directly responsible for the electrocatalytic electron transfer inhibition, an estimate of the free, ion-unpaired Fc+ surface concentration shows that it cannot be directly related to the electron transfer rate. This suggests that the principal reason of the anion-induced electron transfer rate modulation might be related to the molecular level changes of the physical and chemical properties as well as the structure of the self-assembled monolayer.

Journal Article↗
PubMed2001

Interactions of cyclic AMP and its dibutyryl analogue with model membrane: X-ray diffraction and Raman spectroscopic study using cubic liquid-crystalline phases of monoolein.

Interactions of adenosine 3':5'-cyclic monophosphate (cAMP) and its dibutyryl analogue, N6,2'-O-dibutyryladenosine 3':5'-cyclic monophosphate (dbcAMP), with a lipid bilayer were studied by small-angle X-ray diffraction (SAXD) and Raman spectroscopy. The cubic Pn3m phase of monoolein (MO) served as a bilayer-based model system. SAXD measurements have indicated that incorporation of approximately 3 wt.% cAMP leaves the phase parameters practically unaltered, whereas the same content of dbcAMP induces the intercubic Pn3m-->Ia3d transition. By applying the concepts of lipid shape parameter and infinite periodic minimal surface to these MO phases, we have suggested that, as opposed to cAMP, dbcAMP associates with the MO bilayer. This conclusion has been supported by the different effects of phase matrix on the Raman shifts of the adenine and phosphate vibrational modes of these two nucleotides. Moreover, Raman spectra have indicated that dbcAMP inserts into the bilayer through the butyryladenine group, positioning dbcAMP preferentially at the polar/apolar interface.

Algorithms↗
PubMed1999

Solubilization of ubiquinone-10 in the lamellar and bicontinuous cubic phases of aqueous monoolein.

Using X-ray diffraction measurements and polarizing microscopy, the solubilization of ubiquinone-10 (UQ10) was investigated in the lamellar and reversed bicontinuous cubic phases of aqueous monoolein (MO, 86 wt% of monooleoylglycerol). At 25 degrees C and UQ10 content below 0.5 wt%, a partial phase diagram of the MO/UQ10/H2O system indicated the same sequence of hydration-induced phases as found in the MO/H2O system. This low amount of coenzyme had no effect on the MO bilayer thickness and swelling behavior of phases, but it promoted thermotropic Q230-->HII phase transition. We suggested that the effect was determined by the UQ10 partitioning into the HII phase regions where the MO chains must be stressed upon the phase transition. At UQ10 contents above 0.5 wt%, a solid 'UQ10-rich' phase appeared inside the initially homogeneous phases within a few days. It was proposed that this process was driven by the coenzyme lateral diffusion in the MO bilayer.

Crystallization↗
PubMed1996

Effects of distearoylphosphatidylglycerol and lysozyme on the structure of the monoolein-water cubic phase: X-ray diffraction and Raman scattering studies.

X-ray diffraction and Raman scattering spectroscopy have been used to study phase transitions and changes in molecular organization of the cubic Pn3m monoolein (MO)-H2O phase upon introducing low amounts of distearoylphosphatidylglycerol (DSPG) and lysozyme (LSZ). X-ray diffraction measurements indicated a phase transition Pn3m-Im3m brought about by DSPG and LSZ, however DSPG also induced formation of the lamellar phase. Raman spectra have demonstrated that incorporation of DSPG into the lipid bilayer decreases the mobility of acyl chains and increases the number of hydrogen-bonded C=O groups of MO. On the other hand, LSZ exerts identical effect on the latter parameter, while no effect on the state of acyl chains order was observed. This result and differential scanning calorimetric measurements indicate that LSZ is located in the water channel system of the cubic phase. The results are discussed on the basis of an infinite periodical lipid bilayer structure and lipid parameter concepts.

Animals↗
PubMed1992

Glucose biosensor based on carbon black strips.

Amperometric biosensors for the determination of beta-D-glucose have been constructed. They were based on a porous matrix of carbon blacks--'Ketjenblack' (KB) and 'Shawinigan black' (SB) wet-proofed with polytetrafluorethylene. Glucose-sensitive elements were prepared by subsequent adsorptional immobilization of 1,1'-dimethylferrocene (DMFc) and nickel-ocene (Nc) on 'Shawinigan black' or tetracyanoquinodimethane (TCNQ) on 'Ketjenblack' together with Penicillium chrysogenum glucose oxidase. Maximum surface concentrations of DMFc, Nc and TCNQ on carbon black electrodes were 95, 116 and 151 nmol cm-2. The biosensor based on KB and TCNQ (KB-TCNQ biosensor) could be used at a potential of 0.5 V (vs. Ag/AgCl reference electrode) in the concentration range up to 7 mM. This biosensor possessed an approximately ten times higher sensitivity than the ones based on SB and DMFc (SB-DMFc biosensor) and on SB and Nc (SB-Nc biosensor) which acted at 0.3 V and 0.05 V, respectively. The biosensors were suitable for practical use longer than one week.

Biosensing Techniques↗