Abstract: Methods and compositions for selectively modifying nucleic acid molecules in biological compositions, including contacting the composition with an inactivating agent having the formula: ##STR1## where each of R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.6, R.sub.7, and R.sub.8 is, independently, H or a monovalent hydrocarbon moiety containing between 1 and 4 carbon atoms, inclusive, provided that R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.6, R.sub.7, and R.sub.8 cannot all be H; R.sub.5 is a divalent hydrocarbon moiety containing between 2 and 4 carbon atoms, inclusive; X is a pharmaceutically acceptable counter-ion; and n is an integer between 1 and 10, inclusive are disclosed.

Abstract: Methods for tissue welding using solders incorporating biologically active agents, such as growth factors or hemostatic agents, have been developed. Improved solder compositions have also been defined, yielding greater bursting strength as a function of protein concentration, and through the use of protein unfolding prior to laser-mediated denaturation and coupling. A method for repair of fistulas has been discovered, using water as a chromophore, in combination with solder concentration, to form columns to fill defects where tissue apposition is not possible. Methods have also been adapted for use with other forms of directed energy, including bipolar electrosurgery and light. Examples demonstrate increased strength of repairs by incorporation of growth factors into solders, alone and as a function of solder concentration. Increased adhesion is obtained through prevention of bleeding by incorporation of hemostatic agents such as thrombin or epinephrine, a vasoconstrictor.