Antyutleniacze i ich aktywność środowiskowa. Wpływ zwiążków drobnomolekularnych na proteinę

The aim of this study was to evaluate the relationships between the chemical structure of tea catechins and their binding affinities to HSA (Human Serum Albumin) by fluorescence quenching method at pH 7.4 and 37°C. The quenching constants (Kq), binding constants (Kb), and free energy changes (∆G0) were determined for the tested systems. The presented study contributes to the current knowledge in the area of protein-ligand binding, particularly tea catechin-HSA interactions.Celem pracy była ocena zależności między strukturą chemiczną katechin herbaty i ich powinowactwem do HSA (albumina ludzkiej surowicy) za pomocą metody wygaszania fluorescencji przy pH 7,4 i w temperaturze 37°C. Dla badanych układów wyznaczono stałą szybkości wygaszania (Kq), stałą wiązania (Kb) i zmiany entalpii swobodnej (∆G0). Prezentowana praca poszerza aktualny stan wiedzy na temat wiązania białko - ligand, zwłaszcza interakcji katechiny - HSA

Antyoksydanty a stres środowiskowy, badania spektralne stabilności substancji naturalnych i ich oddziaływanie z molekułą białka

The stability of eight hydroxycinnamic acids (HCAs) during long-term incubation under physiological conditions was studied by UV-VIS absorption spectroscopy and their possibility of binding to a model protein (bovine serum albumin, BSA) under physiological conditions was investigated by tryptophan fluorescence quenching method. The obtained results suggest that the stability of hydroxycinnamic acids is dependent upon its individual structure and duration of incubation. The monosubstituted derivatives (coumaric acids) were stable within the course of long-term incubation, while di- and trisubstituted derivatives decomposed easily. It was found out that all studied compounds changed fluorescence emission spectrum of BSA. The Stern-Volmer analysis was employed in order to explore binding of HCAs to BSA in details. The binding constants (Kb), number of binding sites (n) and the free energy changes (∆G0) were determined. The binding affinity was strongest for rosmarinic acid and ranked in the following order rosmarinic acid > chlorogenic acid > sinapic acid > caffeic acid > ferulic acid > o-coumaric acid > p-coumaric acid > m-coumaric acid. All free energy changes (∆G0) possessed negative sign indicating the spontaneity of HCAs binding to BSA.Badano trwałość ośmiu kwasów hydrooksycynamonowych, HCAs, podczas inkubacji długoterminowej w warunkach fizjologicznych i możliwość ich wiązania się z modelowym białkiem (albuminą, BSA). Uzyskane wyniki pokazały, że trwałość tych kwasów zależy od ich indywidualnej budowy oraz czasu inkubacji. Wyznaczono stałe trwałości (Kb), liczbę miejsc wiązania (n) oraz zmianę wartości energii Gibbsa (∆G0) wiązania HCAs do BSA, który to proces przebiegał samorzutnie

The temperature dependence of the helical twist of DNA.

DNA is the carrier of all cellular genetic information and increasingly used in nanotechnology. Quantitative understanding and optimization of its functions requires precise experimental characterization and accurate modeling of DNA properties. A defining feature of DNA is its helicity. DNA unwinds with increasing temperature, even for temperatures well below the melting temperature. However, accurate quanti-tation of DNA unwinding under external forces and a microscopic understanding of the corresponding structural changes are currently lacking. Here we combine single-molecule magnetic tweezers measurements with atomistic molecular dynamics and coarse-grained simulations to obtain a comprehensive view of the temperature dependence of DNA twist. Experimentally, we find that DNA twist changes by Tw(T) = (−11.0 ± 1.2)◦/(◦C·kbp), independent of applied force, in the range of forces where torque-induced melting is negligible. Our atomistic simulations predict Tw(T) = (−11.1 ± 0.3)◦/(◦C·kbp), in quantitative agreement with experiments, and suggest that the untwisting of DNA with temperature is predominantly due to changes in DNA structure for defined backbone substates, while the effects of changes in substate populations are minor. Coarse-grained simulations using the oxDNA framework yield a value of Tw(T) = (−6.4 ± 0.2)◦/(◦C·kbp) in semi-quantitative agreement with experiments