O određivanju olova merkaptobenztiazolom u nazočnosti barija

U nazocnosti tamponske smjese NH40H + NH4N03 moguce je talozenjem merkaptobenztiazolom odrediti olovo i uz stostruku kolicinu barija. Temperatura pri filtraciji taloga ne utjece na rezultate, kao sto na njih ne utjece ni razrjedenje otopine na deseterostruki volumen

O određivanju olova merkaptobenztiazolom u nazočnosti barija

U nazocnosti tamponske smjese NH40H + NH4N03 moguce je talozenjem merkaptobenztiazolom odrediti olovo i uz stostruku kolicinu barija. Temperatura pri filtraciji taloga ne utjece na rezultate, kao sto na njih ne utjece ni razrjedenje otopine na deseterostruki volumen

. Rearrangements of Water Dimer and Hexamer

Abstract. Rearrangement mechanisms of the water dimer and the cage form of the water hexamer are examined theoretically with particular reference to tunneling splittings and spectroscopy. The three lowest barrier rearrangements of the water dimer are characterized by ab initio methods and compared with the results of previous constrained calculations. The acceptor-tunneling pathway does not proceed via a direct rotation around the C2 axis of the acceptor, but rather via relatively asynchronous rotation of the donor about the hydrogen bond and an associated ‘wag’ of the acceptor. Rearrangements between different cage isomers of the water hexamer are studied for two empirical potentials. The experimentally observed triplet splittings may be the result of flip and bifurcation rearrangements of the two single-donor, single-acceptor monomers. Twodimensional quantum calculations of the nuclear dynamics suggest that delocalization over more than one cage isomer may occur, especially in excited states

Free radicals and antioxidants at a glance using EPR spectroscopy

The delicate balance between the advantageous and detrimental effects of free radicals is one of the important aspects of human (patho)physiology. The controlled production of reactive oxygen and nitrogen species has an essential role in the regulation of various signaling switches. On the other hand, imbalanced generation of radicals is highly correlated with the pathogenesis of many diseases which require the application of selected antioxidants to regain the homeostasis. In the era of growing interest for redox processes, electron paramagnetic resonance (EPR) spectroscopy is arguably the best-suited technique for such research due to its ability to provide a unique insight into the world of free radicals and antioxidants. Herein, I present the principles of EPR spectroscopy and the applications of this method in assessing: (i) the oxidative status of biological systems, using endogenous long-lived free radicals (ascorbyl radical (Asc(center dot)), tocopheroxyl radical (TO center dot), melanin) as markers; (ii) the production of short-lived radicals (hydroxyl radical (OH center dot), superoxide radical anion (O-2(-)), sulfur-and carbon-centered radicals), which are implicated in both, oxidative stress and redox signaling; (iii) the metabolism of nitric oxide (NO center dot); (iv) the antioxidative properties of various drugs, compounds, and natural products; (v) other redox-relevant parameter. Besides giving a comprehensive survey of up-to-date literature, I also provide illustrative examples in sufficient detail to provide a means to exploit the potential of EPR in biochemical/physiological/medical research. The emphasis is on the features and characteristics (both positive and negative) relevant for EPR application in clinical sciences. My aim is to encourage fellow colleagues interested in free radicals and antioxidants to expand their base knowledge or methods used in their laboratories with data acquired by EPR or some of the EPR techniques outlined in this review, in order to boost up the exciting area of redox science