Abstract: Assays for the DNA repair protein O.sup.6 -methylguanine-DNA methyltransferase (MGMT) are provided which employ monoclonal antibodies prepared using MGMT having transferase activity, as opposed to denatured MGMT or MGMT fragments. The monoclonal antibodies are able to recognize MGMT in single cell preparations (immunohistochemical staining assays) and in cell extracts (immunoassays). In connection with immunohistochemical staining, the use of a fluorescent readout coupled with digitization of the cell image allows for quantitative measures of MGMT levels in, for example, tumor biopsy samples. Such quantitative measures can be used to determine which patients are likely to benefit from chemotherapy using alkylating agents since tumor cells having low MGMT levels are more likely to be killed by such agents than those with high MGMT levels.

Abstract: A method for tanning skin is provided in which liposomes containing a DNA repair enzyme are administered to skin in combination with exposure of the skin to UV radiation. The result is an enhanced level of melanin production, i.e., more tanning than achieved by UV radiation alone. The administration of the DNA repair enzymes in liposomes also reduces the level of DNA damage caused by the UV exposure. Accordingly, both the tanning response is increased and the deleterious effect of UV exposure is decreased. The method can be used by the general population as well as by individuals whose skin is susceptible to UV-induced damage.

Abstract: Methods for purifying DNA repair enzymes are provided in which an aqueous solution of a DNA repair enzyme in an impure state is applied to a molecular sieve column having an exclusion limit which will retard the DNA repair enzyme but will not retard contaminants larger than the DNA repair enzyme. The DNA repair enzyme in an enhanced state of purity is eluted isocratically from the molecular sieve column in an elution buffer and applied directly to a DNA affinity column in the same buffer without intermediate dialysis, ultrafiltration, or other procedures. The DNA repair enzyme is eluted from the DNA affinity column using, for example, a salt gradient. The method is rapid, inexpensive, simple to perform, and has been found to produce a homogeneous final product. In accordance with other aspects of the invention, the purified DNA repair enzymes are encapsulated in liposomes and administered to living cells in situ.

Abstract: Methods for purifying DNA repair enzymes are provided in which an aqueous solution of a DNA repair enzyme in an impure state is applied to a molecular sieve column having an exclusion limit which will retard the DNA repair enzyme but will not retard contaminants larger than the DNA repair enzyme. The DNA repair enzyme in an enhanced state of purity is eluted isocratically from the molecular sieve column in an elution buffer and applied directly to a DNA affinity column in the same buffer without intermediate dialysis, ultrafiltration, or other procedures. The DNA repair enzyme is eluted from the DNA affinity column using, for example, a salt gradient. The method is rapid, inexpensive, simple to perform, and has been found to produce a homogeneous final product. In accordance with other aspects of the invention, the purified DNA repair enzymes are encapsulated in liposomes and administered to living cells in situ.

Abstract: A method for administering a protein having intracellular biological activity into the interior of living skin cells, which lie below the skin's stratum corneum, is provided. The method comprises the steps of: (a) encapsulating the protein in liposomes; and (b) applying the liposomes to the outer surface of living skin so that the protein encapsulated in the liposomes traverses the skin's stratum corneum and the outer membranes of said cells and is thereby delivered by the liposomes into the interior of said cells. In certain preferred embodiments, the liposomes are pH sensitive liposomes. In other preferred embodiments, the protein is a DNA repair enzyme, such as T4 endonuclease V.

Abstract: Methods for purifying DNA repair enzymes are provided in which an aqueous solution of a DNA repair enzyme in an impure state is applied to a molecular sieve column having an exclusion limit which will retard the DNA repair enzyme but will not retard contaminants larger than the DNA repair enzyme. The DNA repair enzyme in an enhanced state of purity is eluted isocratically from the molecular sieve column in an elution buffer and applied directly to a DNA affinity column in the same buffer without intermediate dialysis, ultrafiltration, or other procedures. The DNA repair enzyme is eluted from the DNA affinity column using, for example, a salt gradient. The method is rapid, inexpensive, simple to perform, and has been found to produce a homogeneous final product. In accordance with other aspects of the invention, the purified DNA repair enzymes are encapsulated in liposomes and administered to living cells in situ.