Patent ID: 8907047

Claim:
A water-soluble polymer, comprising: a repeating unit represented by Formula (1): (wherein R 1 is —COOH, —OH, or —(OCH 2 CH 2 ) p R′ (wherein R′ is —COOH, —OH, —CH═CH 2 , —C≡CH, or —N 3 , and p is an integer from 1 to 30.), and 1 is an integer from 1 to 10.), a repeating unit represented by Formula (2): (wherein R 2 is —SR 3 or —NHR 4 (wherein R 3 is hydrogen or a thiol-protecting group selected from the group consisting of benzyl, methoxybenzyl, N-(acetyl)aminomethyl, t-butyl, methylbenzyl, 3,4-dimethylbenzyl, triphenylmethyl, benzhydryl, acetamidomethyl, carbomethoxysulfenyl, 3-nitro-2-pyridinesulfenyl, ethylcarbamoyl, 9-fluorenylmethyl, and pyridyl sulfide, and R 4 is hydrogen or an amino-protecting group selected from the group consisting of tert-butoxycarbonyl, benzyloxycarbonyl, 9-fluorenylmethyloxycarbonyl, 2,2,2-trichloroethoxycarbonyl, allyloxycarbonyl, phthaloyl, p-toluenesulfonyl, and 2-nitrobenzenesulfonyl); a, the number of repeating units containing —SR 3 , and b, the number of repeating units containing —NHR 4 , in y, the number of repeating units, satisfy b/a+b=0 to 0.60; and m and n are an integer from 1 to 10.), and a repeating unit represented by Formula (3): wherein x, the number of repeating units of Formula (1), y, the number of repeating units of Formula (2), and z, the number of repeating units of said Formula (3), satisfy x/(x+y+z)=0.01 to 0.70, y/(x+y+z)=0.20 to 0.70, and z/(x+y+z)=0.01 to 0.70.