Finding intermodel H-bonds Finding intramodel H-bonds Constraints relaxed by 0.4 angstroms and 20 degrees Models used: #0 4a9a_A.cif H-bonds (donor, acceptor, hydrogen, D..A dist, D-H..A dist): THR 3.A N SER 1.A OG no hydrogen 3.285 N/A GLU 5.A N SER 1.A O no hydrogen 2.903 N/A LYS 6.A N THR 2.A O no hydrogen 2.729 N/A LYS 8.A N VAL 4.A O no hydrogen 3.487 N/A ALA 9.A N GLU 5.A O no hydrogen 3.131 N/A ILE 10.A N LYS 6.A O no hydrogen 3.336 N/A GLU 11.A N ILE 7.A O no hydrogen 2.986 N/A ASP 12.A N LYS 8.A O no hydrogen 2.867 N/A GLU 13.A N ALA 9.A O no hydrogen 3.087 N/A MET 14.A N ILE 10.A O no hydrogen 3.010 N/A ALA 15.A N GLU 11.A O no hydrogen 3.164 N/A ARG 16.A N ASP 12.A O no hydrogen 3.313 N/A ARG 16.A N GLU 13.A O no hydrogen 3.198 N/A THR 17.A N MET 14.A O no hydrogen 3.293 N/A THR 17.A OG1 GLU 13.A O no hydrogen 2.709 N/A GLN 18.A N GLN 18.A OE1 no hydrogen 3.052 N/A ASN 20.A N THR 23.A OG1 no hydrogen 2.966 N/A THR 23.A N ASN 20.A O no hydrogen 3.281 N/A THR 23.A N ASN 20.A OD1 no hydrogen 2.893 N/A THR 23.A OG1 GLN 18.A O no hydrogen 2.854 N/A THR 23.A OG1 ASN 20.A O no hydrogen 3.405 N/A THR 23.A OG1 ASN 20.A OD1 no hydrogen 3.253 N/A SER 24.A OG LYS 21.A O no hydrogen 3.196 N/A HIS 26.A NE2 GLU 13.A OE2 no hydrogen 2.779 N/A LEU 27.A N THR 23.A O no hydrogen 2.940 N/A GLY 28.A N SER 24.A O no hydrogen 2.822 N/A GLN 29.A N PHE 25.A O no hydrogen 2.955 N/A GLN 29.A NE2 ALA 195.A O no hydrogen 3.152 N/A LEU 30.A N HIS 26.A O no hydrogen 2.797 N/A LYS 31.A N LEU 27.A O no hydrogen 2.995 N/A LYS 31.A NZ ASP 216.A OD1 no hydrogen 2.995 N/A LYS 31.A NZ ASP 216.A OD2 no hydrogen 3.410 N/A ALA 32.A N GLY 28.A O no hydrogen 3.168 N/A LYS 33.A N GLN 29.A O no hydrogen 2.758 N/A LYS 33.A NZ GLU 199.A OE1 no hydrogen 3.331 N/A LYS 33.A NZ GLU 199.A OE2 no hydrogen 2.797 N/A LEU 34.A N LEU 30.A O no hydrogen 2.785 N/A ALA 35.A N LYS 31.A O no hydrogen 2.892 N/A LYS 36.A N ALA 32.A O no hydrogen 3.036 N/A LYS 36.A NZ GLU 199.A O no hydrogen 2.753 N/A LEU 37.A N LYS 33.A O no hydrogen 3.125 N/A ARG 38.A N LEU 34.A O no hydrogen 3.017 N/A ARG 39.A N ALA 35.A O no hydrogen 3.089 N/A ARG 39.A NE GLU 223.A OE1 no hydrogen 2.928 N/A ARG 39.A NE GLU 223.A OE2 no hydrogen 3.299 N/A GLU 40.A N LYS 36.A O no hydrogen 3.161 N/A LEU 41.A N ARG 38.A O no hydrogen 3.258 N/A LEU 42.A N ARG 39.A O no hydrogen 2.988 N/A THR 43.A N GLU 40.A O no hydrogen 3.281 N/A THR 43.A OG1 ARG 39.A O no hydrogen 3.275 N/A THR 43.A OG1 GLU 40.A O no hydrogen 3.468 N/A SER 44.A OG LEU 42.A O no hydrogen 2.927 N/A GLY 47.A N ASP 51.A OD2 no hydrogen 2.792 N/A ILE 48.A N THR 129.A OG1 no hydrogen 2.930 N/A GLY 49.A N VAL 52.A O no hydrogen 2.796 N/A PHE 50.A N GLY 47.A O no hydrogen 2.909 N/A ASP 51.A N GLY 47.A O no hydrogen 2.694 N/A THR 55.A N GLN 107.A OE1 no hydrogen 3.483 N/A VAL 57.A N LYS 105.A O no hydrogen 3.017 N/A SER 59.A N ASN 131.A OD1 no hydrogen 2.704 N/A SER 59.A OG GLN 107.A OE1 no hydrogen 2.700 N/A VAL 60.A N GLN 107.A O no hydrogen 2.808 N/A GLY 61.A N LEU 132.A O no hydrogen 2.943 N/A PHE 62.A N LEU 109.A O no hydrogen 2.791 N/A VAL 63.A N PHE 134.A O no hydrogen 2.868 N/A LYS 70.A N SER 67.A OG no hydrogen 2.974 N/A LYS 70.A NZ ASP 110.A OD2 no hydrogen 3.377 N/A SER 71.A N SER 67.A O no hydrogen 3.123 N/A SER 71.A OG SER 67.A O no hydrogen 3.396 N/A THR 72.A N VAL 68.A O no hydrogen 3.036 N/A THR 72.A OG1 VAL 68.A O no hydrogen 2.867 N/A LEU 73.A N GLY 69.A O no hydrogen 2.912 N/A LEU 74.A N LYS 70.A O no hydrogen 3.032 N/A SER 75.A N SER 71.A O no hydrogen 3.101 N/A SER 75.A OG SER 71.A O no hydrogen 3.068 N/A SER 75.A OG SER 82.A OG no hydrogen 3.060 N/A LYS 76.A N THR 72.A O no hydrogen 2.842 N/A LYS 76.A NZ SER 261.A O no hydrogen 2.581 N/A LYS 76.A NZ ASP 264.A OD1 no hydrogen 2.634 N/A LEU 77.A N LEU 73.A O no hydrogen 2.848 N/A THR 78.A N LEU 74.A O no hydrogen 3.069 N/A THR 78.A OG1 LEU 74.A O no hydrogen 2.912 N/A THR 78.A OG1 PRO 96.A O no hydrogen 3.419 N/A GLY 79.A N SER 75.A O no hydrogen 2.818 N/A SER 82.A N SER 75.A OG no hydrogen 3.177 N/A SER 82.A OG SER 75.A OG no hydrogen 3.060 N/A GLU 83.A N GLU 86.A OE2 no hydrogen 2.910 N/A GLU 86.A N GLU 83.A O no hydrogen 2.806 N/A TYR 87.A N ALA 84.A O no hydrogen 3.174 N/A THR 94.A N ASP 110.A O no hydrogen 3.067 N/A ILE 99.A N ILE 106.A O no hydrogen 2.873 N/A ARG 100.A NH1 GLY 103.A O no hydrogen 3.197 N/A TYR 101.A N ALA 104.A O no hydrogen 2.933 N/A ALA 104.A N TYR 101.A O no hydrogen 2.842 N/A ILE 106.A N ILE 99.A O no hydrogen 2.744 N/A GLN 107.A N ALA 58.A O no hydrogen 2.982 N/A GLN 107.A NE2 ALA 53.A O no hydrogen 2.819 N/A MET 108.A N GLY 97.A O no hydrogen 2.915 N/A LEU 109.A N VAL 60.A O no hydrogen 2.788 N/A ASP 110.A N THR 94.A O no hydrogen 2.850 N/A LEU 111.A N PHE 62.A O no hydrogen 2.893 N/A GLY 113.A N LEU 92.A O no hydrogen 2.980 N/A ILE 114.A N LEU 111.A O no hydrogen 3.203 N/A ILE 115.A N PRO 112.A O no hydrogen 2.891 N/A LYS 121.A NZ LEU 41.A O no hydrogen 3.121 N/A GLN 122.A N ARG 119.A O no hydrogen 3.153 N/A GLN 122.A NE2 ASP 51.A OD1 no hydrogen 2.751 N/A VAL 123.A N ARG 119.A O no hydrogen 3.398 N/A ILE 124.A N GLY 120.A O no hydrogen 3.434 N/A ALA 125.A N LYS 121.A O no hydrogen 2.909 N/A VAL 126.A N GLN 122.A O no hydrogen 2.948 N/A ALA 127.A N VAL 123.A O no hydrogen 2.849 N/A ARG 128.A N ILE 124.A O no hydrogen 2.892 N/A ARG 128.A NH1 VAL 156.A O no hydrogen 3.010 N/A ARG 128.A NH1 SER 226.A O no hydrogen 2.980 N/A ARG 128.A NH2 SER 226.A O no hydrogen 2.905 N/A THR 129.A N VAL 126.A O no hydrogen 2.990 N/A THR 129.A OG1 ALA 125.A O no hydrogen 2.840 N/A THR 129.A OG1 VAL 126.A O no hydrogen 3.112 N/A CYS 130.A N ALA 127.A O no hydrogen 3.306 N/A CYS 130.A SG VAL 126.A O no hydrogen 3.558 N/A ASN 131.A N SER 59.A O no hydrogen 2.835 N/A LEU 133.A N PRO 231.A O no hydrogen 3.064 N/A PHE 134.A N GLY 61.A O no hydrogen 2.715 N/A ILE 135.A N ILE 233.A O no hydrogen 2.852 N/A ILE 136.A N VAL 63.A O no hydrogen 2.904 N/A LEU 137.A N VAL 235.A O no hydrogen 2.783 N/A VAL 139.A N ASN 237.A O no hydrogen 2.994 N/A ASN 140.A N ASP 138.A OD1 no hydrogen 2.777 N/A LYS 141.A N ASP 138.A O no hydrogen 2.795 N/A LYS 146.A N PRO 142.A O no hydrogen 2.984 N/A LYS 146.A NZ GLU 150.A OE1 no hydrogen 2.826 N/A LYS 146.A NZ GLU 150.A OE2 no hydrogen 2.832 N/A GLN 147.A N LEU 143.A O no hydrogen 2.958 N/A ILE 148.A N HIS 144.A O no hydrogen 3.290 N/A ILE 149.A N HIS 145.A O no hydrogen 3.044 N/A GLU 150.A N LYS 146.A O no hydrogen 2.934 N/A LYS 151.A N GLN 147.A O no hydrogen 3.018 N/A LYS 151.A NZ GLU 11.A OE2 no hydrogen 3.311 N/A GLU 152.A N ILE 148.A O no hydrogen 2.971 N/A LEU 153.A N ILE 149.A O no hydrogen 2.954 N/A GLU 154.A N GLU 150.A O no hydrogen 2.794 N/A GLY 155.A N LYS 151.A O no hydrogen 2.796 N/A VAL 156.A N LEU 153.A O no hydrogen 3.095 N/A GLY 157.A N GLU 154.A O no hydrogen 2.792 N/A ILE 158.A N LEU 153.A O no hydrogen 3.117 N/A ARG 159.A N ARG 228.A O no hydrogen 2.902 N/A ARG 159.A NE ASP 220.A OD1 no hydrogen 3.226 N/A ARG 159.A NE ASP 220.A OD2 no hydrogen 3.100 N/A ARG 159.A NH1 GLU 154.A O no hydrogen 2.971 N/A ARG 159.A NH1 ILE 158.A O no hydrogen 2.952 N/A ARG 159.A NH2 ASP 220.A OD1 no hydrogen 3.261 N/A ASN 161.A N MET 230.A O no hydrogen 2.804 N/A ASN 161.A ND2 ALA 232.A O no hydrogen 3.033 N/A ILE 167.A N PRO 165.A O no hydrogen 3.043 N/A LEU 168.A N ALA 208.A O no hydrogen 3.027 N/A LYS 170.A N GLU 206.A O no hydrogen 2.765 N/A LYS 172.A N SER 204.A O no hydrogen 2.951 N/A LYS 172.A NZ GLU 206.A OE1 no hydrogen 3.396 N/A SER 178.A N ALA 205.A O no hydrogen 2.861 N/A THR 180.A N ILE 207.A O no hydrogen 2.774 N/A ASN 181.A ND2 VAL 183.A O no hydrogen 2.559 N/A THR 182.A N PHE 209.A O no hydrogen 2.860 N/A THR 182.A OG1 PHE 209.A O no hydrogen 3.161 N/A THR 186.A N ASP 212.A OD1 no hydrogen 2.682 N/A THR 186.A OG1 ASP 212.A OD1 no hydrogen 3.247 N/A THR 186.A OG1 ASP 212.A OD2 no hydrogen 2.620 N/A GLY 189.A N GLU 192.A OE1 no hydrogen 3.247 N/A GLU 192.A N ASP 191.A OD1 no hydrogen 2.662 N/A ILE 193.A N GLY 189.A O no hydrogen 3.167 N/A ARG 194.A N ASN 190.A O no hydrogen 2.820 N/A ALA 195.A N ASP 191.A O no hydrogen 2.797 N/A VAL 196.A N GLU 192.A O no hydrogen 3.024 N/A MET 197.A N ILE 193.A O no hydrogen 2.936 N/A SER 198.A N ARG 194.A O no hydrogen 2.893 N/A SER 198.A OG ARG 194.A O no hydrogen 2.628 N/A SER 198.A OG ALA 195.A O no hydrogen 3.116 N/A GLU 199.A N ALA 195.A O no hydrogen 3.212 N/A TYR 200.A N VAL 196.A O no hydrogen 3.000 N/A TYR 200.A OH GLU 223.A OE2 no hydrogen 2.619 N/A ARG 201.A N SER 198.A O no hydrogen 2.778 N/A ARG 201.A NH1 GLU 199.A O no hydrogen 2.719 N/A ARG 201.A NH1 GLU 199.A OE2 no hydrogen 2.949 N/A ILE 202.A N MET 197.A O no hydrogen 2.843 N/A SER 204.A OG LYS 174.A O no hydrogen 2.524 N/A SER 204.A OG GLY 176.A O no hydrogen 2.746 N/A ALA 205.A N GLY 176.A O no hydrogen 3.109 N/A GLU 206.A N LYS 170.A O no hydrogen 2.602 N/A ILE 207.A N SER 178.A O no hydrogen 2.882 N/A ALA 208.A N LEU 168.A O no hydrogen 2.754 N/A PHE 209.A N THR 180.A O no hydrogen 2.829 N/A ARG 210.A N ASP 166.A O no hydrogen 2.983 N/A CYS 211.A SG ASP 166.A O no hydrogen 3.654 N/A ALA 213.A N CYS 211.A O no hydrogen 2.703 N/A THR 214.A N ASP 217.A OD2 no hydrogen 2.953 N/A LEU 218.A N THR 214.A O no hydrogen 3.206 N/A ILE 219.A N VAL 215.A O no hydrogen 3.090 N/A ASP 220.A N ASP 216.A O no hydrogen 2.728 N/A VAL 221.A N ASP 217.A O no hydrogen 3.111 N/A LEU 222.A N LEU 218.A O no hydrogen 3.062 N/A GLU 223.A N ILE 219.A O no hydrogen 2.771 N/A ALA 224.A N VAL 221.A O no hydrogen 3.091 N/A SER 226.A N GLU 223.A O no hydrogen 3.210 N/A SER 226.A OG GLU 223.A O no hydrogen 3.510 N/A ARG 227.A N GLU 223.A O no hydrogen 3.199 N/A ARG 227.A NE ASP 220.A OD1 no hydrogen 3.095 N/A ARG 228.A N GLY 157.A O no hydrogen 3.024 N/A ARG 228.A NH1 SER 225.A O no hydrogen 3.256 N/A ARG 228.A NH1 ARG 227.A O no hydrogen 3.005 N/A ARG 228.A NH2 SER 225.A O no hydrogen 3.562 N/A MET 230.A N ARG 159.A O no hydrogen 2.922 N/A ALA 232.A N ASN 161.A OD1 no hydrogen 2.990 N/A ILE 233.A N LEU 133.A O no hydrogen 2.782 N/A TYR 234.A N ASN 255.A O no hydrogen 2.709 N/A TYR 234.A OH GLU 150.A OE2 no hydrogen 2.521 N/A VAL 235.A N ILE 135.A O no hydrogen 2.803 N/A LEU 236.A N VAL 257.A O no hydrogen 3.081 N/A ASN 237.A N LEU 137.A O no hydrogen 2.781 N/A ASN 237.A ND2 SER 261.A OG no hydrogen 2.946 N/A LYS 238.A N ASN 237.A OD1 no hydrogen 2.804 N/A ILE 239.A N ILE 259.A O no hydrogen 3.251 N/A ASP 240.A N ASP 240.A OD1 no hydrogen 2.497 N/A SER 241.A N LYS 238.A O no hydrogen 3.197 N/A LEU 242.A N ILE 239.A O no hydrogen 2.758 N/A SER 243.A OG GLU 246.A OE1 no hydrogen 2.693 N/A GLU 245.A N GLU 245.A OE1 no hydrogen 2.746 N/A GLU 246.A N SER 243.A OG no hydrogen 3.079 N/A LEU 247.A N SER 243.A O no hydrogen 2.851 N/A GLU 248.A N ILE 244.A O no hydrogen 2.884 N/A LEU 249.A N GLU 245.A O no hydrogen 3.040 N/A LEU 250.A N GLU 246.A O no hydrogen 3.185 N/A LEU 250.A N LEU 247.A O no hydrogen 2.983 N/A TYR 251.A N GLU 248.A O no hydrogen 3.027 N/A TYR 251.A OH GLU 269.A OE1 no hydrogen 2.461 N/A ARG 252.A N LEU 249.A O no hydrogen 3.002 N/A ILE 253.A N LEU 250.A O no hydrogen 2.912 N/A VAL 257.A N TYR 234.A O no hydrogen 2.859 N/A ILE 259.A N LEU 236.A O no hydrogen 2.898 N/A SER 260.A N TRP 265.A O no hydrogen 3.269 N/A SER 261.A N ASN 237.A OD1 no hydrogen 2.892 N/A SER 261.A OG GLY 69.A O no hydrogen 3.339 N/A GLN 263.A N SER 260.A OG no hydrogen 2.905 N/A ASP 264.A N SER 260.A O no hydrogen 2.904 N/A ASN 266.A ND2 PRO 258.A O no hydrogen 2.817 N/A LEU 267.A N ASP 264.A O no hydrogen 3.176 N/A GLU 269.A N ASP 268.A OD1 no hydrogen 2.583 N/A LEU 270.A N ASN 266.A O no hydrogen 2.817 N/A LEU 271.A N LEU 267.A O no hydrogen 3.135 N/A GLN 272.A N ASP 268.A O no hydrogen 2.995 N/A GLN 272.A NE2 GLN 272.A O no hydrogen 3.363 N/A GLN 272.A NE2 ASP 276.A OD1 no hydrogen 3.295 N/A VAL 273.A N GLU 269.A O no hydrogen 2.862 N/A MET 274.A N LEU 270.A O no hydrogen 3.017 N/A TRP 275.A N LEU 271.A O no hydrogen 2.908 N/A ASP 276.A N GLN 272.A O no hydrogen 2.924 N/A ARG 277.A N VAL 273.A O no hydrogen 2.923 N/A ARG 277.A NH1 ASN 161.A OD1 no hydrogen 3.459 N/A ARG 277.A NH1 ALA 232.A O no hydrogen 3.559 N/A ARG 277.A NH2 ASN 161.A OD1 no hydrogen 2.553 N/A LEU 278.A N MET 274.A O no hydrogen 3.066 N/A LEU 278.A N TRP 275.A O no hydrogen 3.231 N/A VAL 281.A N LEU 300.A O no hydrogen 2.933 N/A ARG 282.A N ASP 347.A OD1 no hydrogen 2.900 N/A ARG 282.A NE ASP 347.A OD1 no hydrogen 2.865 N/A ARG 282.A NH2 ASP 347.A OD1 no hydrogen 3.465 N/A ARG 282.A NH2 ASP 347.A OD2 no hydrogen 2.626 N/A ILE 283.A N VAL 298.A O no hydrogen 2.868 N/A TYR 284.A N ASP 349.A O no hydrogen 3.051 N/A TYR 284.A OH GLU 348.A OE2 no hydrogen 2.732 N/A LYS 286.A N VAL 351.A O no hydrogen 3.118 N/A LYS 286.A NZ PRO 287.A O no hydrogen 3.275 N/A LYS 286.A NZ LYS 288.A O no hydrogen 3.267 N/A THR 295.A OG1 ASP 293.A O no hydrogen 3.195 N/A THR 295.A OG1 ASP 293.A OD2 no hydrogen 3.561 N/A ASP 296.A N ASP 293.A OD2 no hydrogen 3.157 N/A VAL 298.A N ILE 283.A O no hydrogen 3.008 N/A LEU 300.A N VAL 281.A O no hydrogen 2.865 N/A SER 302.A OG LEU 278.A O no hydrogen 3.240 N/A ARG 304.A N ARG 301.A O no hydrogen 3.048 N/A CYS 305.A SG ARG 301.A O no hydrogen 3.641 N/A CYS 305.A SG SER 302.A O no hydrogen 3.459 N/A CYS 305.A SG LEU 345.A O no hydrogen 3.649 N/A SER 306.A N ASP 309.A OD2 no hydrogen 2.823 N/A SER 306.A OG ASP 309.A OD2 no hydrogen 2.755 N/A VAL 307.A N HIS 343.A O no hydrogen 2.786 N/A LYS 308.A N LEU 341.A O no hydrogen 2.742 N/A ASP 309.A N SER 306.A OG no hydrogen 2.930 N/A PHE 310.A N SER 306.A O no hydrogen 2.821 N/A CYS 311.A N VAL 307.A O no hydrogen 2.868 N/A CYS 311.A SG VAL 307.A O no hydrogen 3.345 N/A ASN 312.A N LYS 308.A O no hydrogen 3.075 N/A GLN 313.A N ASP 309.A O no hydrogen 2.912 N/A ILE 314.A N PHE 310.A O no hydrogen 3.170 N/A ILE 314.A N CYS 311.A O no hydrogen 2.959 N/A HIS 315.A N CYS 311.A O no hydrogen 2.937 N/A HIS 315.A ND1 SER 317.A OG no hydrogen 2.962 N/A SER 317.A N HIS 315.A ND1 no hydrogen 3.269 N/A SER 317.A OG HIS 315.A ND1 no hydrogen 2.962 N/A LEU 318.A N HIS 315.A O no hydrogen 3.286 N/A ASP 320.A N SER 317.A O no hydrogen 2.909 N/A ASP 321.A N LEU 318.A O no hydrogen 3.211 N/A PHE 322.A N VAL 319.A O no hydrogen 3.354 N/A ARG 323.A N LEU 354.A O no hydrogen 2.852 N/A ALA 325.A N VAL 339.A O no hydrogen 3.058 N/A LEU 326.A N THR 352.A O no hydrogen 2.804 N/A VAL 327.A N GLN 337.A O no hydrogen 2.992 N/A TYR 328.A N VAL 350.A O no hydrogen 2.960 N/A GLY 329.A N GLN 335.A OE1 no hydrogen 2.678 N/A SER 330.A OG GLU 346.A OE1 no hydrogen 2.656 N/A SER 331.A OG HIS 343.A NE2 no hydrogen 2.963 N/A SER 331.A OG ASP 349.A OD1 no hydrogen 3.415 N/A SER 331.A OG ASP 349.A OD2 no hydrogen 2.591 N/A VAL 332.A N GLY 329.A O no hydrogen 3.291 N/A GLN 335.A NE2 GLY 329.A O no hydrogen 2.816 N/A GLN 337.A N VAL 327.A O no hydrogen 2.993 N/A VAL 339.A N ALA 325.A O no hydrogen 2.837 N/A HIS 343.A N GLY 340.A O no hydrogen 2.957 N/A HIS 343.A NE2 SER 331.A OG no hydrogen 2.963 N/A LEU 345.A N CYS 305.A O no hydrogen 2.877 N/A GLU 346.A N ASP 349.A OD2 no hydrogen 2.730 N/A GLU 348.A N ARG 282.A O no hydrogen 2.626 N/A ASP 349.A N GLU 346.A O no hydrogen 2.953 N/A VAL 350.A N TYR 328.A O no hydrogen 2.865 N/A VAL 351.A N TYR 284.A O no hydrogen 2.951 N/A THR 352.A N LEU 326.A O no hydrogen 2.868 N/A THR 352.A OG1 LYS 286.A O no hydrogen 2.831 N/A LEU 354.A N ASN 324.A O no hydrogen 2.770 N/A LYS 356.A N ASP 321.A O no hydrogen 2.749 N/A