We have used electronic absorption and fluorescence spectroscopy to study binding between a platinum(II) dimethylsulfoxide complex (cis-[Pt(DMSO) 2 Cl 2 ]) and human serum albumin (HSA), and the effect of complexation on the structure of the protein. We have calculated the binding parameters for binding between cis-[Pt(DMSO) 2 Cl 2 ] and HSA. We have determined the binding constant K B = (1.2 ± 0.1)⋅10 3 M -1 and the Hill coefficient h = 1.03 ± 0.1. We have determined that binding between cis-[Pt(DMSO) 2 Cl 2 ] and the protein leads to a change in the internal packing of the macromolecule. Introduction. As we know [1, 2], cisplatin (cis-[Pt(NH 3 ) 2 Cl 2 ]) is used as an effective drug for treatment of cancers: ovarian tumors, sarcomas, breast cancer, and prostate cancer. However, the therapeutic action of the drug is accompanied by various side effects (vomiting, nephrotoxicity, neurotoxicity, alopecia, ototoxicity, etc.) which are due to inactivation of proteins. Biotransformation of cisplatin in the body occurs by binding platinum to serum albumin [3]. This protein can reversibly bind to drugs and biologically active substances and is distinguished by rather low ligand-protein binding selectivity. It has been established that binding with the active centers of albumin occurs as a result of different types of interactions: hydrophobic, dipole, electrostatic, via van der Waals forces, hydrogen bonds. Complexes formed in this case are unstable and readily dissociated; the binding energy is no greater than 8-10 kcal/mol, which allows the ligands to easily interact with other substances [4]. The problem is complex because the structural diversity of drugs requires an individual approach to experimental assessment of these interactions, taking into account the spectral, physicochemical, and structural characteristics of the studied drug.In order to reduce the toxicity of cancer drugs based on Pt(II), sulfur-containing ligands (thiols, thiocarbamates) are used in third-generation drugs [5,6]. In this work, as the sulfur-containing compound we selected dimethylsulfoxide (DMSO), which has unique biomedical and pharmacological properties: it penetrates through biological membranes, improves transport properties of drugs, stimulates the immune system, and reduces the effects of chemotherapy and radiation therapy [7,8].Experimental Section. We used human serum albumin (HSA) from Sigma Chemical (USA), a solution of 0.9% sodium chloride (physiological saline) from the pharmaceutical company Likvor (Armenia). Cis-[Pt(DMSO) 2 Cl 2 ] was synthesized as in [9]. In all the experiments, we used a 0.9% sodium chloride solution to prepare the protein solutions. The protein concentration (0.4 mg/mL) in solution was determined using electronic absorption spectra in the UV region (UV spectroscopy), where we used the molar absorption coefficient ε = 36.500 M -1 ⋅cm -1 for λ = 280 nm [10]. The concentration of cis-[Pt(DMSO) 2 Cl 2 ] was varied within the range (0-5)⋅10 -5 M. The electronic absorption spectra of the solutions were mea...

Ascorbic acid in dimethyl-and diethylsulfoxide solutions has been studied using vibrational (Fourier transform IR and Raman) spectroscopy. Noticeable changes observed in the range of S=O-group vibrations can be explained by the presence of a hydrogen bond between ascorbic acid and sulfoxides. Various types of ascorbic acid/sulfoxide hydrogen-bonded complexes were revealed based on spectral analysis data. The results showed that the ascorbic acid/dimethylsulfoxide system has predominantly one type of complexes whereas the ascorbic acid/diethylsulfoxide system can contain three types of complexes.Introduction. Ascorbic acid (AA) is better known as vitamin C and is the focus of several scientific research groups [1][2][3][4][5][6]. Dimethylsulfoxide (DMSO) is widely used in both biology and medicine [7,8]. The biological significance of diethylsulfoxide (DESO) has been demonstrated [9, 10]. The urgency for investigating AA-DMSO (DESO) systems stems from the fact that AA acts as a cryoprotector, like DMSO and DESO. Furthermore, it has been shown [11] that AA in combination with DMSO enhances the effective cryopreservation of cells. It is noteworthy that DMSO and DESO can penetrate living tissue without causing damage [9] and that AA maintains skin elasticity. Thus, it was expected based on the known property of DMSO as an effective drug transporter [7,8] that DMSO (or DESO) solutions of AA would increase its transport. Recently Fourier-transform IR spectroscopy with attenuated total internal reflectance (ATIR) was used to find the transport effectiveness of AA through skin [1]. The study of AA-DMSO (DESO) solutions is also important for revealing the nature of the intermolecular interaction and understanding the mechanism of their biological activity.Herein the existence of various intermolecular AA-DMSO (DESO) complexes is proven using IR and Raman spectroscopy.Experimental. DESO was prepared and purified according to the literature method [12]. The purity of the product was tested using GC >99.5% purity, <0.01% water content after drying over molecular sieves). DMSO (Aldrich Chemical Co.) was dried over molecular sieves and distilled at reduced pressure. Ascorbic acid (Aldrich Chemical Co., 99.5%) was used as received.IR spectra of pure AA were obtained using a mineral oil mull and drops between KBr plates. Solutions were prepared by direct mixing of a known quantity of DESO, DMSO, and AA at concentrations of 0.25, 0.50, and 1.00 M. IR spectra of pure AA and solutions in DESO and DMSO were recorded using a Fourier-transform Nicolet/NEXUS spectrometer with a CsJ beam divider in the range 4000-220 cm -1 with resolution 4 cm -1 and 32 scans.Raman spectra were recorded on an IFS66-FRA106 (Bruker Instrument Co.) Fourier-transform spectrometer. The laser power on the sample was ≈200 mW at λ = 1064 nm. Each Raman spectrum was the average of 2000 scans with spectrometer resolution 2 cm -1 . Measurements were made in a cell with a thermostatted holder at sample temperature 25 o C (±1 o C). The reproducibility of the Raman...

Liquid-vapor phase equilibria in dimethyl sulfoxide-alkanol (1-propanol, 1-butanol, and tertbutanol) binary systems are studied using a static method. The total saturated vapor pressure in the temperature range of 293.15-323.15 K is measured. The partial pressures of dimethyl sulfoxide and alkanes have been calculated via integrating the Gibbs-Duhem equation. Excess molar Gibbs energies are described by the Redlich-Kister equation, and the correlation parameters are calculated. The nature of the deviation from the ideal behavior of these solutions is explained by allowing for the presence of competing homo-and heteromolecular interactions and the considerable effect of the length of the alkanols' hydrocarbon chains has on the values of the thermodynamic parameters.

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The effect of the concentration of sodium di-(2-ethylhexyl) sulfosuccinate (AOT) on the volume and transport properties of the AOT/n-heptane/dimethylsulfoxide-water reverse micellar systems at different sulfoxide to water volume ratios, constant degree of AOT hydration R = 10, and temperatures of 298.15-313.15 K was studied by densimetry and viscosimetry. The apparent volumes of the polar phases and the volume fractions of micelles were calculated using the densities of these systems. In the presence of dimethylsulfoxide, an increase in its concentration led to an increase in the apparent volume of the polar phase; an increase in the AOT concentration at increased viscosity of the system led to a decrease in the apparent volume of the micellar nucleus.