Emergence of highly-designable protein-backbone conformations in an off-lattice model

Despite the variety of protein sizes, shapes, and backbone configurations found in nature, the design of novel protein folds remains an open problem. Within simple lattice models it has been shown that all structures are not equally suitable for design. Rather, certain structures are distinguished by unusually high designability: the number of amino-acid sequences for which they represent the unique ground state; sequences associated with such structures possess both robustness to mutation and thermodynamic stability. Here we report that highly designable backbone conformations also emerge in a realistic off-lattice model. The highly designable conformations of a chain of 23 amino acids are identified, and found to be remarkably insensitive to model parameters. While some of these conformations correspond closely to known natural protein folds, such as the zinc finger and the helix-turn-helix motifs, others do not resemble known folds and may be candidates for novel fold design.Comment: 7 figure

Deriving N-soliton solutions via constrained flows

The soliton equations can be factorized by two commuting x- and t-constrained flows. We propose a method to derive N-soliton solutions of soliton equations directly from the x- and t-constrained flows.Comment: 8 pages, AmsTex, no figures, to be published in Journal of Physics

Constructing N-soliton solution for the mKdV equation through constrained flows

Based on the factorization of soliton equations into two commuting integrable x- and t-constrained flows, we derive N-soliton solutions for mKdV equation via its x- and t-constrained flows. It shows that soliton solution for soliton equations can be constructed directly from the constrained flows.Comment: 10 pages, Latex, to be published in "J. Phys. A: Math. Gen.

Indefinite survival of rat islet allografts following infusion of donor bone marrow without cytoablation

We have tested the effect of donor bone marrow cell (DBMC) infusion on the survival of pancreatic islet allografts in the rat, without the use of cytoablative recipient conditioning. Lewis and diabetic Brown Norway rats were used as donors and recipients, respectively. Donor islets were placed beneath the left renal capsule. Infusion of DBMC and temporary immunosuppression followed by delayed islet transplantation resulted in indefinite survival of all islet grafts (MST >180 days). Control animals demonstrated recurrent hyperglycemia (islet allografts rejection). Donor bone marrow derived cells were detected in the spleen and cervical lymph nodes of BN recipients of LEW bone marrow but not in the recipients of islet transplants alone. Second set full thickness skin grafts were performed in normal BN and in recipients of a previously successful ITX. Donor specific skin grafts were accepted in the animals that had received DBMC 40 days before the islet allograft, while animals receiving DBMC at the time of the islet allograft rejected the donor specific skin graft similarly to the controls. However, these animals did not reject a second set donor-specific islet transplant. The results indicate that radiation conditioning of the recipients was not necessary to induce microchimerism and graft acceptance in this rodent model of islet allotransplantation