Format of *.rsa-Files produced by NACCESS

A residue accessibility (.rsa) file containing summed atomic accessible surface areas over each protein residue, as well as the relative accessibility of each residue calculated as the %accessiblity compared to the accessibility of that residue type in an extended ALA-x-ALA tripeptide. See Hubbard, Campbell & Thornton (1991) J.Mol.Biol.220,507-530.

The beginning and end of an example .rsa file are shown below. The data is summed over residues, and split into 5 classes. Total (all atoms), Non Polar Sidechain (all non-oxygens and non-nitrogens in the sidechain), Polar Sidechain (all oxygens and nitrogens in the sidechain), total sidechain, and mainchain. For our purposes, alpha carbons are classed as sidechain atoms, so that glycine can have a sidechain accessibility. They are therefore not included in the mainchain. For each class, two values are given, an absolute (ABS) and relative (REL) accessibility. The absolute value is the simple sum, whilst the REL value is the % relative accessiblity. Absolute sums over the whole chain are also given.

REM  Relative accessibilites read from external file "/apl/progs/naccess/standard.data"
REM  File of summed (Sum) and % (per.) accessibilities for 
REM RES _ NUM      All atoms   Non P side   Polar Side   Total Side   Main Chain
REM                ABS   REL    ABS   REL    ABS   REL    ABS   REL    ABS   REL
RES ASP A   1   117.56  83.7  22.87  47.6  40.85  74.9  63.72  62.1  53.84 142.4
RES ILE A   2    13.46   7.7  12.60   9.1   0.00   0.0  12.60   9.1   0.86   2.3
RES VAL A   3    99.31  65.6  98.07  85.9   0.00   0.0  98.07  85.9   1.24   3.3
RES LEU A   4    14.63   8.2   0.00   0.0   0.00   0.0   0.00   0.0  14.63  38.9
RES THR A   5    77.54  55.7  53.98  72.4  23.56  87.0  77.54  76.3   0.00   0.0
RES GLN A   6    17.45   9.8   0.26   0.5   0.00   0.0   0.26   0.2  17.19  45.7
RES SER A   7    44.18  37.9  32.45  69.3  10.37  33.1  42.83  54.8   1.36   3.5
RES PRO A   8    47.06  34.6  46.26  38.7   0.00   0.0  46.26  38.7   0.81   5.0
RES SER A   9    88.12  75.6  43.57  93.0  33.25 106.1  76.83  98.3  11.29  29.4
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END  Absolute sums over accessible surface 
TOTAL         65311.6      34690.3      18554.4      53244.7       9761.9