Tag Archive for Vovk

Carbohydrate Polymers, 2017, 169, 117–126

N.G. Voron’ko, S.R. Derkach, M.A. Vovk, P.M. Tolstoy

“Complexation of κ-carrageenan with gelatin in the aqueous phase analysed by 1H NMR kinetics and relaxation”

Carbohydrate Polymers, 2017, 169, 117–126
DOI: 10.1016/j.carbpol.2017.04.010

The 1H NMR spectroscopy is used to study the kinetics of gelation in the aqueous mixtures of κ-carrageenan with gelatin. The time dependence of NMR signals intensities shows that the kinetics of gel formation consists of classical ‘fast’ (rate constant k ≈ 6 h−1) and ‘slow’ (k ≈ 1 h−1) periods, corresponding to a coil → helix transition and subsequent aggregation of helices. Upon increase of the κ-carrageenan/gelatin (w/w) ratio Z the rate of the fast process slows down by a factor of 1.6–2.4. Further analysis was done by studying the dependence of spin-spin relaxation times of protons of gelatin on Z in the aqueous phase. A qualitative scheme describing hydrogel formation in the complex solution is given. It is hypothesized that at higher concentration of PECs the hydrogel structure network is stabilized by three types of nodes: triple helices of gelatin and intra-/inter-molecular double helices of κ-carrageenan.


Mikhail Vovk has presented an excursion-lecture about modern NMR spectroscopy methods for high school students. The equipments presented in CMR and some aspect of its application were demonstrated during the excursion.

DPX 300

Trableshoting of cooling sistem of Bruker DPX 300.

Colloid Surface A, 2017, 518, 273-282

A.S. Koneva, E.A. Safonova, P.S. Kondrakhina, M.A. Vovk, A.A. Lezov, Yu.S. Chernyshev, N.A. Smirnova

“Effect of water content on structural and phase behavior ofwater-in-oil (n-decane) microemulsion system stabilized by mixednonionic surfactants SPAN 80/TWEEN 80”

Colloid Surface A, 2017, 518, 273-282

For the search of effective microemulsion systems with the properties demanded for various applica-tions the knowledge of structural properties of the reverse microemulsions for various compositionsand temperatures is of high value. In the present study, the microstructure and diffusion of the compo-nents of water-in-n-decane Winsor IV microemulsions stabilized by a mixture of nonionic surfactantsSpan 80 (sorbitane monooleate, HLB 4.9) and Tween 80 (polyoxyethylene sorbitan monooleate, HLB15.0) at the weight ratios 49:51 (i.e. at the maximal ability to solubilize water) were investigatedby viscosimetry, PGSTE NMR and DLS. The system phase diagram obtained at 298.2 K includes theintermediate heterogeneous region between the reverse micelles region and the microemulsions. Thewater-to-surfactant molar ratio was changed up to 15.5 (13 wt.% of water) at the weight ratios n-decane:surfactants 65:35 and 85:15. The microemulsion droplets are spherical (that is corresponded also to thecryo-TEM data) and grow with the increase of water content. The temperature effect on the aggregatesdiffusion (and on the aggregates size) in the range 298.2–318.2 K is not pronounced. The bimodal distri-butions of the diffusion coefficients determined using both DLS and PGSTE NMR methods are specific for the system. The slower diffusion mode relates to the diffusion of mixed microemulsion droplets with theradii Rh ∼10–20 nm. The second stable form of nanoaggregates are “dry” micelles with Rh ∼ 1–2 nm. Thedata on the diffusion coefficients are of special interest in particular for the molecular dynamic simulationof the reverse micelles or of the microemulsion droplets.



Stanislav Sukharzhevskii and Mikhail Vovk have presented a lecture-excursion for second year students of the Faculty of Physics.

Trophy of training course

Michael Vovk has successfully completed the training course “Advanced NMR Methods”. The course covered the uses of gradients, different options of shimming, set of 1D, 2D and 3D homonuclear and heteronuclear correlation experiments with gradient selection and water suppression, other aspects of modern NMR methods.

Excursion for high-school students

Michael Vovk has presented a lecture for students of Academic gymnasium. Our guests acquainted with the magnetic resonance research methods and modern equipment represented in CMR.


Open Doors Day, Institute of Chemistry

At an Open Day of Institute of Chemistry (SPBU) Michael Vovk has presented a lecture-excursion for high school students about modern NMR methods and equipments.

Excursion-lecture for “LETI” students

Excursion-lecturer was conducted in the Center for Magnetic Resonance for Saint-Petersburg Electrotechnical University (“LETI”) students. Equipment for modern NMR techniques were demonstrated by Mikhail Vovk, demonstration of operation on the EPR spectrometer Bruker Elexsys E580 was conducted by Stanislav Sukharzhevskii.

Excursion for first year students

Mikhail Vovk has conducted a lecture for first year students of physical faculty.