Still other particular embodiments are those in which the compound has formula (I), wherein P1 is selected from ???NHC(O)NH???, ???OC(O)NH??? and ???NHC(O)O???; n is 0; m is 1; L1 is selected from unsubstituted C1-C6 alkylene; L2 is selected from substituted or unsubstituted C1-C6 alkylene; and P3 is selected from ???C(O)NHR2, ???C(O)NHS(O)2R2, ???NHS(O)2R2, and ???C(O)OR2, wherein R2 is a member