Purification and administration of DNA repair enzymes
First Claim
1. A process for producing a liposome-encapsulated DNA repair enzyme comprising:
- (a) growing cells which synthesize the DNA repair enzyme;
(b) preparing an extract of the cells which contains the DNA repair enzyme in an impure state;
(c) contacting the extract with a molecular sieve having an exclusion limit which is (i) larger than the molecular weight of the DNA repair enzyme and (ii) smaller than the molecular weight of at least some of the impurities in the extract such that the DNA repair enzyme will pass through the molecular sieve at a slower rate than at least some of said impurities;
(d) isocratically eluting the DNA repair enzyme from the molecular sieve with an aqueous elution solution so as to obtain the DNA repair enzyme in one or more selected fractions of the eluate in a state of enhanced purity, said aqueous elution solution being chosen so that complexes can form between the DNA repair enzyme and selected nucleic acids;
(e) without further purification, contacting the one or more selected fractions from step (d) in said aqueous elution solution with one or more selected nucleic acids which have been immobilized on a solid support so as to form immobilized nucleic-acid/DNA-repair-enzyme complexes between the DNA repair enzyme and the one or more selected, immobilized nucleic acids;
(f) washing the immobilized complexes to remove at least some of the remaining impurities;
(g) eluting the DNA repair enzyme from the one or more selected, immobilized nucleic acids so as to obtain the DNA repair enzyme in one or more selected fractions of the eluate in a state of further enhanced purity; and
(h) encapsulating at least a portion of the purified DNA repair enzyme contained in the one or more selected fractions of step (g) in pH sensitive liposomes.
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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. This form of administration has been found to be non-toxic to the cells and to result in increased incision of damaged DNA, enhanced DNA repair synthesis, and increased cell survival after exposure to ultraviolet light. In certain preferred embodiments, DNA repair enzymes are administered in pH sensitive liposomes.
81 Citations
22 Claims
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1. A process for producing a liposome-encapsulated DNA repair enzyme comprising:
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(a) growing cells which synthesize the DNA repair enzyme; (b) preparing an extract of the cells which contains the DNA repair enzyme in an impure state; (c) contacting the extract with a molecular sieve having an exclusion limit which is (i) larger than the molecular weight of the DNA repair enzyme and (ii) smaller than the molecular weight of at least some of the impurities in the extract such that the DNA repair enzyme will pass through the molecular sieve at a slower rate than at least some of said impurities; (d) isocratically eluting the DNA repair enzyme from the molecular sieve with an aqueous elution solution so as to obtain the DNA repair enzyme in one or more selected fractions of the eluate in a state of enhanced purity, said aqueous elution solution being chosen so that complexes can form between the DNA repair enzyme and selected nucleic acids; (e) without further purification, contacting the one or more selected fractions from step (d) in said aqueous elution solution with one or more selected nucleic acids which have been immobilized on a solid support so as to form immobilized nucleic-acid/DNA-repair-enzyme complexes between the DNA repair enzyme and the one or more selected, immobilized nucleic acids; (f) washing the immobilized complexes to remove at least some of the remaining impurities; (g) eluting the DNA repair enzyme from the one or more selected, immobilized nucleic acids so as to obtain the DNA repair enzyme in one or more selected fractions of the eluate in a state of further enhanced purity; and (h) encapsulating at least a portion of the purified DNA repair enzyme contained in the one or more selected fractions of step (g) in pH sensitive liposomes. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 16)
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- 15. A composition comprising pH sensitive liposomes having a DNA repair enzyme encapsulated therein.
Specification