The influences of the conformational changes on the mechanisms of generation of rotational strengths in near-UV of TEM-1 beta-lactamase are studied theoretically by the matrix method on the base of X-ray structures of the free enzyme and protein components of four enzyme-ligand complexes. The changes of the aromatic and disulfide contributions are estimated and the trends for realizations of the known mechanisms of generation of rotational strengths are described. (C) 2004 Elsevier B.V. All rights reserved.