* Bs-CspB and Bc-Csp are small, monomeric proteins of 67 and 66 residues, respectively.

* Without disulfide bonds, cofactors or tightly bound ligands.Both proteins unfold reversibly in two-state reaction, make an excellent pair of models for identifying the origins of thermostability.

* Bs-CspB and Bc-Csp differ in sequence at 12 positions, all of which map to the protein surface.