The enzyme, ribonucleotide reductase, catalyses the formation of deoxyribonucleotides from ribonucleotides, a reaction essential for DNA synthesis in all living cells. The Escherichia coli ribonucleotide reductase, which is the prototype of all known eukaryotic and virus-coded enzymes, consists of two nonidentical subunits, proteins B1 and B2. The B2 subunit contains an antiferromagnetically co...

collection of multiple processes that increase the chronological age of an organism leading to death is defined as aging, and even though important, it is poorly understood. recent research has shown that aging is due to biochemical and genetic changes, in interaction with environmental effects, including diet and nutrition. most knowledge on aging is based on ge­netic model system, but its mol...

background & aim: medicinal plants can be a good replacement for common cancer treatment including chemotherapy, radiation therapy and surgery because they don’t have many side effects. the aim of this study was to investigate the effect of temperature on the free radical scavenging in the presence of medicinal plants. experimental: for determination of free radical scavenging activity was...

Free radical cyclizations of the 4-phenylbutyl radical and analogues carrying naphthyl and vinyl groups instead of phenyl have been studied. A typical reaction scheme is given below involving closures to fiveand six-membered rings. Competition rate studies for the various types of ring closure were performed with deuterated analogues. The results can be used as an efficient mechanistic tool for...

Phleomycin induces DNA breakage in vitro in the presence of the sulphydryl compound dithiothreitol. The reaction appears to be free radical-mediated, and requires oxygen and metal ions. Reaction rate is limited by the concentration of oxygen, which is converted to hydrogen peroxide during DNA breakage. However there is no net change in the sulphydryl compound. The proposed reaction mechanism in...

reactions of free radicals and reactive oxygen species (ros) with biological molecules in vivo play an important physiological role in many diseases. 2,2-diphenyl-1-picrylhydrazyl (dpph) is a stable free radical and often used as a routine reagent to evaluate the antioxidant capacity of an antioxidant. this study was undertaken to investigate the free radical-scavenging and antioxidant activiti...

Tin-free Giese reactions, employing primary, secondary, and tertiary alkyl iodides as radical precursors, ethyl acrylate as a radical trap, and sodium cyanoborohydride as a radical mediator, were examined in a continuous flow system. With the use of an automated flow microreactor, flow reaction conditions for the Giese reaction were quickly optimized, and it was found that a reaction temperatur...

the first reaction between food components and biological tissues occurs in the oral cavity. saliva modulates the ecosystem in the oral cavity and plays a critical role in oral homeostasis. in addition, saliva is a first line of defense against free radical-mediated stress. salivary antioxidant defense mechanisms seem to be very important. in this study we discuss in detail free radicals (fr) a...