Gallium has been employed (in the form of soluble salts) to fight various forms of cancer, infectious, and inflammatory diseases. The rationale behind this lies in the ability of Ga(3+) cation to mimic closely in appearance the native ferric ion, Fe(3+), thus interfering with the biological processes requiring ferric cofactors. However, Ga(3+) ion cannot participate in redox reactions and, when substituting for the "native" Fe(3+) ion in the enzyme active site, renders it inactive. Although a significant body of information on the Ga(3+)-Fe(3+) competition in biological systems has been accumulated, the intimate mechanism of the process is still not well understood and several questions remain: What are the basic physical principles governing the competition between the two trivalent cations in proteins? What type of metal centers are the most likely targets for gallium therapy? To what extent are the Fe(3+)-binding sites in the key enzyme ribonucleotide reductase vulnerable to Ga(3+) substitution? Here, we address these questions by studying the competition between Ga(3+) and Fe(3+) ions in model metal binding sites of various compositions and charge states. The results obtained are in line with available experimental data and shed light on the intimate mechanism of the Ga(3+)/Fe(3+) selectivity in various model metal binding sites and biological systems such as serum transferrin and ribonucleotide reductase.
Аннотация. Исследованы слабоустойчивые состояния и особенности структурных изменений в области фазовых переходов на примере би-нарного сплава Cu 3 Au. Выявлены особенности термоактивируемых перестроек структуры на микро-, нано-и макроструктурных уровнях бинарного сплава Cu 3 Au при отклонении от стехиометрического состава. Показано, что в окрестности структурно-фазовых превращений в сплавах Cu 3 Au в области 75 % Cu (ат.) реализуются слабоустойчивые состояния, в которых наблюдается целый спектр аномальных явле-ний, подготавливающих систему к превращению.Ключевые слова: слабоустойчивые состояния, структурные перестройки, фазовые переходы.
LOW-STABILITY PRE-TRANSIONAL STATES, PHASE ORDER-DISORDER TRANSION AND STRUCTURAL TRANSFORMATION IN Cu 3 Au ALLOYAbstract. The low-stability states and structural peculiarities in the phase transition area of the Cu 3 Au binary alloy are investigated. The thermal reconstruction characteristics of the binary alloy in case of its stoichiometric composition deviation were revealed on the micro, nano and macro structural scales. It is shown that in the vicinity of the structural phase transition of the Cu 3 Au alloy at the 25 at. % Au domain the low-stability states arise which exhibits the whole range of abnormal phenomena responsible for the system transformation inducement.
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