Subunit Characteristics of Pig Pancreas Ferritin Revealed by MALDI-TOF MS and RP-HPLC

Pig pancreas ferritin（PPF） was purified by ultra-centrifugation, ion-exchange chromatography, and native gradient polyacrylamide gel electrophoresis（PAGENG）. Sodium dodecyl sulfate（SDS）-PAGE indicates that PPF consists of two subunit types, namely, H（21000） and L（19000） subunits, and its core shows an average element composition of 1698 Fe3＋ and 179 phosphate molecules within the hollow shell, giving a 9.5：1 ratio of Fe3＋ to phosphate. An off line approach combining reversed-phase high-performance liquid chromatography（RP-HPLC） with matrix-assisted laser desorption ionization time of flight mass spectrometry（MALDI-TOF MS） made the decomposition of PPF shell into H and L subunits for the analysis of mass spectrometry（MS）, giving molecular weights of both H（21014.4） and L（18319.9） subunits. Both subunit types were further identified by an approach combining peptide mass fingerprint（PMF） with database search. A ratio of 1H to 2L subunits in PPF was determined by SDS-PAGE, RP-HPLC, and MALDI-TOF MS, respectively. It is well known that the non-covalent interaction of L-L or H-L subunits is stronger than that of H-H subunits in PPF, which may be further used to explain the unclear physiological function between H and L subunits in PPF.     

SmFeAsO0.78F0.22中Mn掺杂对超导电性的抑制效应

本文报道了Mn替代Fe对最佳掺杂的Sm-1111体系超导电性的影响.通过电输运及磁性质的测量发现Mn对Fe的替代迅速抑制了超导电性.随着Mn含量的增加,体系的电阻率ρ和磁化率M逐渐增大.对于低掺杂x＜0.25%和未掺杂样品,M接近零,对于≤1%,M从室温到超导转变几乎不变,实验指出Fe2+失去其磁性.我们提出这是由于F...