Lack of toxicity, excellent solubility and superb biocompatibility make polyethylene glycol (PEG) one of the most popular modifiers of biologicals. The most common method for attachment of PEG is based on modification of amino groups of proteins with methoxy- or succinimide-derivatives of PEG. In the case of proteins with amino groups important for biological activity, this modification can lead to inactivation of proteins. A new strategy for covalent attachment of PEG to carboxylic groups of proteins using O,O-bis-(2-aminopropyl)polyethylene glycol and carbodiimide/N-hydroxysuccinimide-mediated reaction was developed. The reaction is carried out under mild aqueous conditions. The attached PEG serves as a hydrophilic spacer for further bioconjungation with biomolecules and haptens. Lipase from Candida rugosa was used as a model protein. Characteristic data of the modified protein such as activity, isoelectric points and stability were compared with that of the unmodified protein.

It is shown by dielectric resonance absorption at 60 GHz that there is a linear coupling of the electric field to the ground state of effective mass acceptors in Si reflecting the lower T(d) symmetry in the central portion of the ground state wave function. The coupling increases strongly with increasing binding energy from B to In, i.e., with decreasing Bohr radius of the acceptor. An unexpected nonlinear Zeeman splitting is observed the magnitude of which also increases from B to In. For all acceptors a central fine structure is found which correlates with the homogeneous linewidth.

It is shown by dielectric resonance absorption at 24 GHz and by ultrasonic resonance spectroscopy between .5 and 10 GHz that linear coupling of the electric field to the ground state of effective mass acceptors in Si exists and has a distinct chemical shift from B to In.