We investigate eigenvalues of many-body systems interacting by two-body forces as well as those of random matrices. For two-body random ensemble, we find a strong linear correlation between ...eigenvalues and diagonal matrix elements if both of them are sorted from the smaller values to larger ones. By using this linear correlation we are able to predict reasonably all eigenvalues of a given Hamiltonian matrix without complicated iterations. For Gaussian orthogonal ensemble matrices, the hyperbolic tangent function improves the accuracy of predicted eigenvalues near the minimum and maximum.
Kinetics of conformational change of a semiflexible polymer under mechanical external field were investigated with Langevin dynamics simulations. It is found that a semiflexible polymer exhibits ...large hysteresis in mechanical folding/unfolding cycle even with a slow operation, whereas in a flexible polymer, the hysteresis almost disappears at a sufficiently slow operation. This suggests that the essential features of the structural transition of a semiflexible polymer should be interpreted at least on a two-dimensional phase space. The appearance of such large hysteresis is discussed in relation to different pathways in the loading and unloading processes. By using a minimal two-variable model, the hysteresis loop is described in terms of different pathways on the transition between two stable states.
Monte Carlo simulation of annealed copolymers of solvophobic/solvophilic monomers show collapsed globular states having dynamic core−shell structures. In these, the core is mostly solvophobic while ...the core boundary contains an excess of solvophilic monomers. This two-state model, where each monomer undergoes interconversion between solvophobic and solvophilic state, is a minimal version of models of neutral water-soluble polymers such as PEO. The reduced surface tension of such core−shell structures suggests an explanation of the stability of PNIPAM globules as observed in the experiments of Wang et al. Wang, X.; Qiu, X.; Wu, C. Macromolecules 1998, 31, 2972. The statistics of the monomeric states along the chain vary with the degree of chain swelling. They are differ from those of quenched copolymers designed to create water-soluble globules though both systems involve a core−shell structure.
Protection of small interfering RNA (siRNA) against degradation and targeted delivery across the plasma and endosomal membranes to the final site of RNA interference (RNAi) are major aims for the ...development of siRNA therapeutics. Targeting for folate receptor (FR)-expressing tumors, we optimized siRNA polyplexes by coformulating a folate-PEG-oligoaminoamide (for surface shielding and targeting) with one of three lipo-oligoaminoamides (optionally tyrosine-modified, for optimizing stability and size) to generate ∼100 nm targeted lipopolyplexes (TLPs), which self-stabilize by cysteine disulfide cross-links. To better understand parameters for improved tumor-directed gene silencing, we analyzed intracellular distribution and siRNA release kinetics. FR-mediated endocytosis and endosomal escape of TLPs was confirmed by immuno-TEM. We monitored colocalization of TLPs with endosomes and lysosomes, and onset of siRNA release by time-lapse confocal microscopy; analyzed intracellular stability by FRET using double-labeled siRNA; and correlated results with knockdown of eGFPLuc protein and EG5 mRNA expression. The most potent formulation, TLP1, containing lipopolyplex-stabilizing tyrosine trimers, was found to unpack siRNA in sustained manner with up to 5-fold higher intracellular siRNA stability after 4 h compared to other TLPs. Unexpectedly, data indicated that intracellular siRNA stability instead of an early endosomal exit dominate as a deciding factor for silencing efficiency of TLPs. After i.v. administration in a subcutaneous leukemia mouse model, TLP1 exhibited ligand-dependent tumoral siRNA retention, resulting in 65% EG5 gene silencing at mRNA level without detectable adverse effects. In sum, tyrosine-modified TLP1 conveys superior protection of siRNA for an effective tumor-targeted delivery and RNAi in vivo.
Nuclear structure of the doublet bands in the doubly-odd nuclei with mass A ∼ 130 is studied in terms of a pair-truncated shell model. The model reproduces quite well the energy levels of the doublet ...bands and the electromagnetic transitions. The doublet bands turn out to be realized by the chopsticks-like motion of two angular momenta of the unpaired neutron and the unpaired proton, weakly coupled with the quadrupole collective excitations of the even-even part of the nucleus.
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