拆分PDB结构，使每条链成为一个单独的pdb结构

说明：parse_pdb_split_chain()函数用于将PDB中包含的链拆开，包括对应的alpha-helix、beta-sheet、links信息 (不足之处在于由于暂时没有遇到含有TURN的PDB结构，所以暂时没有获取对应的turn信息)。

import gzip
import re

def parse_pdb_split_chain(pdbgzFile,outpath):
    with gzip.open(pdbgzFile,rb) as pdbF:
        pdbcontent = pdbF.read()
        pdbcontent = pdbcontent.decode()

        pattern = re.compile(ATOMs+d+s*w+s*[A-Z]{3,4}s*(w)s*.+
,re.MULTILINE)
        match = list(set(list(pattern.findall(pdbcontent))))

        for chain in match:
            patt_helix = re.compile((HELIXs+w+s*w+s*[A-Z]{3,4}s*+chain+s*.+)
,re.MULTILINE)
            patt_sheet = re.compile((SHEETs+w+s*w+s*w+s*[A-Z]{3,4}s*+chain+s*.+)
,re.MULTILINE)
            patt_links = re.compile((LINKs+w+s*w+s*+chain+s*.+)
,re.MULTILINE)
            patt_cha = re.compile((ATOMs+d+s*w+s*[A-Z]{3,4}s*+chain+s*.+)
,re.MULTILINE)
            
            match_helix = patt_helix.findall(pdbcontent)
            match_sheet = patt_sheet.findall(pdbcontent)
            match_links = patt_links.findall(pdbcontent)
            match_cha = patt_cha.findall(pdbcontent)
            
            outfile = outpath+pdbgzFile.split(/)[-1].split(.)[0][3:].upper()+_+chain+.pdb
            outF = open(outfile,w)
            for i in range(len(match_helix)):  ## alpha-helix
                outF.write(match_helix[i]+
) 
            for j in range(len(match_sheet)):  ## beta-sheet
                outF.write(match_sheet[j]+
)
            for k in range(len(match_links)):  ## Links
                outF.write(match_links[k]+
)
            for l in range(len(match_cha)):  ## ATOM
                outF.write(match_cha[l]+
)
            outF.write(TER
)
            outF.write(END
)
            outF.close()

pdbgzFile：指的是PDB的压缩文件。

outpath: 指的是结果的输出目录。

输出文件的命名方式是：PDBID_chainID.pdb