WHAT IF Check report

This file was created 2011-12-13 from WHAT_CHECK output by a conversion script. If you are new to WHAT_CHECK, please study the pdbreport pages. There also exists a legend to the output.

Please note that you are looking at an abridged version of the output (all checks that gave normal results have been removed from this report). You can have a look at the Full report instead.

Verification log for pdb3bkl.ent

Checks that need to be done early-on in validation

Warning: Ligands for which a topology was generated automatically

The topology for the ligands in the table below were determined automatically. WHAT IF uses a local copy of Daan van Aalten's Dundee PRODRG server to automatically generate topology information for ligands. For this PDB file that seems to have gone fine, but be aware that automatic topology generation is a complicated task. So, if you get messages that you fail to understand or that you believe are wrong, and one of these ligands is involved, then check the ligand topology first.

 591 ACT   ( 705-)  A  -
 592 ACT   ( 706-)  A  -
 595 KAW   ( 800-)  A  -
 596 ACT   ( 708-)  A  -

Administrative problems that can generate validation failures

Warning: Groups attached to potentially hydrogenbonding atoms

Residues were observed with groups attached to (or very near to) atoms that potentially can form hydrogen bonds. WHAT IF is not very good at dealing with such exceptional cases (Mainly because it's author is not...). So be warned that the hydrogenbonding-related analyses of these residues might be in error.

For example, an aspartic acid can be protonated on one of its delta oxygens. This is possible because the one delta oxygen 'helps' the other one holding that proton. However, if a delta oxygen has a group bound to it, then it can no longer 'help' the other delta oxygen bind the proton. However, both delta oxygens, in principle, can still be hydrogen bond acceptors. Such problems can occur in the amino acids Asp, Glu, and His. I have opted, for now to simply allow no hydrogen bonds at all for any atom in any side chain that somewhere has a 'funny' group attached to it. I know this is wrong, but there are only 12 hours in a day.

 584 NAG   ( 693-)  A  -   O4  bound to  585 NAG   ( 694-)  A  -   C1

Coordinate problems, unexpected atoms, B-factor and occupancy checks

Warning: Unexpected atoms encountered

While reading the PDB file, at least one atom was encountered that was not expected in the residue. This might be caused by a naming convention problem. It can also mean that a residue was found protonated that normally is not (e.g. aspartic acid). The unexpected atoms have been discarded; in case protons were deleted that actually might be needed, they will later be put back by the hydrogen bond validation software. This normally is not a warning you should worry too much about.

Warning: What type of B-factor?

WHAT IF does not yet know well how to cope with B-factors in case TLS has been used. It simply assumes that the B-factor listed on the ATOM and HETATM cards are the total B-factors. When TLS refinement is used that assumption sometimes is not correct. TLS seems not mentioned in the header of the PDB file. But anyway, if WHAT IF complains about your B-factors, and you think that they are OK, then check for TLS related B-factor problems first.

Obviously, the temperature at which the X-ray data was collected has some importance too:

Crystal temperature (K) :100.000

Nomenclature related problems

Warning: Arginine nomenclature problem

The arginine residues listed in the table below have their N-H-1 and N-H-2 swapped.

 134 ARG   ( 173-)  A
 147 ARG   ( 186-)  A
 214 ARG   ( 253-)  A
 447 ARG   ( 489-)  A

Warning: Tyrosine convention problem

The tyrosine residues listed in the table below have their chi-2 not between -90.0 and 90.0

 107 TYR   ( 146-)  A
 136 TYR   ( 175-)  A
 174 TYR   ( 213-)  A
 220 TYR   ( 259-)  A
 320 TYR   ( 360-)  A
 350 TYR   ( 390-)  A
 439 TYR   ( 481-)  A
 450 TYR   ( 492-)  A
 481 TYR   ( 523-)  A
 553 TYR   ( 595-)  A

Warning: Phenylalanine convention problem

The phenylalanine residues listed in the table below have their chi-2 not between -90.0 and 90.0.

 157 PHE   ( 196-)  A
 254 PHE   ( 293-)  A
 276 PHE   ( 316-)  A
 282 PHE   ( 322-)  A
 283 PHE   ( 323-)  A
 295 PHE   ( 335-)  A
 325 PHE   ( 365-)  A
 351 PHE   ( 391-)  A
 430 PHE   ( 472-)  A
 554 PHE   ( 596-)  A

Warning: Glutamic acid convention problem

The glutamic acid residues listed in the table below have their chi-3 outside the -90.0 to 90.0 range, or their proton on OE1 instead of OE2.

 163 GLU   ( 202-)  A

Geometric checks

Warning: Possible cell scaling problem

Comparison of bond distances with Engh and Huber [REF] standard values for protein residues and Parkinson et al [REF] values for DNA/RNA shows a significant systematic deviation. It could be that the unit cell used in refinement was not accurate enough. The deformation matrix given below gives the deviations found: the three numbers on the diagonal represent the relative corrections needed along the A, B and C cell axis. These values are 1.000 in a normal case, but have significant deviations here (significant at the 99.99 percent confidence level)

There are a number of different possible causes for the discrepancy. First the cell used in refinement can be different from the best cell calculated. Second, the value of the wavelength used for a synchrotron data set can be miscalibrated. Finally, the discrepancy can be caused by a dataset that has not been corrected for significant anisotropic thermal motion.

Please note that the proposed scale matrix has NOT been restrained to obey the space group symmetry. This is done on purpose. The distortions can give you an indication of the accuracy of the determination.

If you intend to use the result of this check to change the cell dimension of your crystal, please read the extensive literature on this topic first. This check depends on the wavelength, the cell dimensions, and on the standard bond lengths and bond angles used by your refinement software.

Unit Cell deformation matrix

 |  0.997832  0.000466  0.000196|
 |  0.000466  0.998582 -0.000187|
 |  0.000196 -0.000187  0.997881|
Proposed new scale matrix

 |  0.016745 -0.000008 -0.000003|
 | -0.000005  0.011776  0.000002|
 | -0.000001  0.000001  0.007428|
With corresponding cell

    A    =  59.718  B   =  84.921  C    = 134.630
    Alpha=  90.021  Beta=  89.977  Gamma=  89.947

The CRYST1 cell dimensions

    A    =  59.849  B   =  85.038  C    = 134.920
    Alpha=  90.000  Beta=  90.000  Gamma=  90.000

Variance: 75.199
(Under-)estimated Z-score: 6.391

Warning: Unusual bond angles

The bond angles listed in the table below were found to deviate more than 4 sigma from standard bond angles (both standard values and sigma for protein residues have been taken from Engh and Huber [REF], for DNA/RNA from Parkinson et al [REF]). In the table below for each strange angle the bond angle and the number of standard deviations it differs from the standard values is given. Please note that disulphide bridges are neglected. Atoms starting with "-" belong to the previous residue in the sequence.

 219 HIS   ( 258-)  A      CA   CB   CG  108.24   -5.6
 219 HIS   ( 258-)  A      CG   ND1  CE1 110.48    4.9
 234 HIS   ( 273-)  A      CG   ND1  CE1 109.72    4.1
 260 ASP   ( 300-)  A      CA   CB   CG  106.71   -5.9
 337 ASP   ( 377-)  A      CA   CB   CG  107.14   -5.5
 388 HIS   ( 428-)  A      CG   ND1  CE1 110.16    4.6
 400 HIS   ( 442-)  A      CG   ND1  CE1 109.68    4.1
 444 TRP   ( 486-)  A      CA   CB   CG  105.92   -4.0
 581 PRO   ( 623-)  A      CD   N    CA  106.23   -4.1

Error: Nomenclature error(s)

Checking for a hand-check. WHAT IF has over the course of this session already corrected the handedness of atoms in several residues. These were administrative corrections. These residues are listed here.

 134 ARG   ( 173-)  A
 147 ARG   ( 186-)  A
 163 GLU   ( 202-)  A
 214 ARG   ( 253-)  A
 447 ARG   ( 489-)  A

Error: Tau angle problems

The side chains of the residues listed in the table below contain a tau angle (N-Calpha-C) that was found to deviate from te expected value by more than 4.0 times the expected standard deviation. The number in the table is the number of standard deviations this RMS value deviates from the expected value.

 372 ALA   ( 412-)  A    4.91
 132 THR   ( 171-)  A    4.10
 125 ASP   ( 164-)  A    4.06

Torsion-related checks

Warning: Torsion angle evaluation shows unusual residues

The residues listed in the table below contain bad or abnormal torsion angles.

These scores give an impression of how `normal' the torsion angles in protein residues are. All torsion angles except omega are used for calculating a `normality' score. Average values and standard deviations were obtained from the residues in the WHAT IF database. These are used to calculate Z-scores. A residue with a Z-score of below -2.0 is poor, and a score of less than -3.0 is worrying. For such residues more than one torsion angle is in a highly unlikely position.

 543 PRO   ( 585-)  A    -2.9
 124 PRO   ( 163-)  A    -2.6
 575 PRO   ( 617-)  A    -2.6
 439 TYR   ( 481-)  A    -2.4
 475 SER   ( 517-)  A    -2.4
 354 TYR   ( 394-)  A    -2.3
 116 GLN   ( 155-)  A    -2.2
 393 LEU   ( 433-)  A    -2.2
 479 ILE   ( 521-)  A    -2.2
 115 PRO   ( 154-)  A    -2.0

Warning: Backbone evaluation reveals unusual conformations

The residues listed in the table below have abnormal backbone torsion angles.

Residues with `forbidden' phi-psi combinations are listed, as well as residues with unusual omega angles (deviating by more than 3 sigma from the normal value). Please note that it is normal if about 5 percent of the residues is listed here as having unusual phi-psi combinations.

  84 GLU   ( 123-)  A  Poor phi/psi
 123 GLU   ( 162-)  A  PRO omega poor
 323 LYS   ( 363-)  A  Poor phi/psi
 391 ASN   ( 431-)  A  Poor phi/psi
 475 SER   ( 517-)  A  Poor phi/psi
 512 GLN   ( 554-)  A  Poor phi/psi
 chi-1/chi-2 correlation Z-score : -1.775

Warning: Unusual backbone conformations

For the residues listed in the table below, the backbone formed by itself and two neighbouring residues on either side is in a conformation that is not seen very often in the database of solved protein structures. The number given in the table is the number of similar backbone conformations in the database with the same amino acid in the centre.

For this check, backbone conformations are compared with database structures using C-alpha superpositions with some restraints on the backbone oxygen positions.

A residue mentioned in the table can be part of a strange loop, or there might be something wrong with it or its directly surrounding residues. There are a few of these in every protein, but in any case it is worth looking at!

  32 THR   (  71-)  A      0
  63 PHE   ( 102-)  A      0
  67 GLN   ( 106-)  A      0
  69 GLN   ( 108-)  A      0
  84 GLU   ( 123-)  A      0
  85 ARG   ( 124-)  A      0
 114 HIS   ( 153-)  A      0
 115 PRO   ( 154-)  A      0
 116 GLN   ( 155-)  A      0
 121 GLN   ( 160-)  A      0
 122 LEU   ( 161-)  A      0
 123 GLU   ( 162-)  A      0
 133 SER   ( 172-)  A      0
 134 ARG   ( 173-)  A      0
 175 VAL   ( 214-)  A      0
 220 TYR   ( 259-)  A      0
 224 HIS   ( 263-)  A      0
 228 GLU   ( 267-)  A      0
 234 HIS   ( 273-)  A      0
 235 LEU   ( 274-)  A      0
 240 TRP   ( 279-)  A      0
 242 GLN   ( 281-)  A      0
 243 THR   ( 282-)  A      0
 244 TRP   ( 283-)  A      0
 245 SER   ( 284-)  A      0
And so on for a total of 170 lines.

Warning: Omega angles too tightly restrained

The omega angles for trans-peptide bonds in a structure are expected to give a gaussian distribution with the average around +178 degrees and a standard deviation around 5.5 degrees. These expected values were obtained from very accurately determined structures. Many protein structures are too tightly restrained. This seems to be the case with the current structure too, as the observed standard deviation is below 4.0 degrees.

Standard deviation of omega values : 2.146

Warning: Unusual PRO puckering phases

The proline residues listed in the table below have a puckering phase that is not expected to occur in protein structures. Puckering parameters were calculated by the method of Cremer and Pople [REF]. Normal PRO rings approximately show a so-called envelope conformation with the C-gamma atom above the plane of the ring (phi=+72 degrees), or a half-chair conformation with C-gamma below and C-beta above the plane of the ring (phi=-90 degrees). If phi deviates strongly from these values, this is indicative of a very strange conformation for a PRO residue, and definitely requires a manual check of the data. Be aware that this is a warning with a low confidence level. See: Who checks the checkers? Four validation tools applied to eight atomic resolution structures [REF].

 124 PRO   ( 163-)  A   -38.4 envelop C-alpha (-36 degrees)
 159 PRO   ( 198-)  A   102.5 envelop C-beta (108 degrees)
 232 PRO   ( 271-)  A   108.5 envelop C-beta (108 degrees)
 272 PRO   ( 312-)  A   116.5 envelop C-beta (108 degrees)
 293 PRO   ( 333-)  A   103.0 envelop C-beta (108 degrees)
 533 PRO   ( 575-)  A    99.3 envelop C-beta (108 degrees)
 575 PRO   ( 617-)  A  -163.2 half-chair N/C-delta (-162 degrees)
 581 PRO   ( 623-)  A  -146.0 envelop C-delta (-144 degrees)

Bump checks

Error: Abnormally short interatomic distances

The pairs of atoms listed in the table below have an unusually short interactomic distance; each bump is listed in only one direction.

The contact distances of all atom pairs have been checked. Two atoms are said to `bump' if they are closer than the sum of their Van der Waals radii minus 0.40 Angstrom. For hydrogen bonded pairs a tolerance of 0.55 Angstrom is used. The first number in the table tells you how much shorter that specific contact is than the acceptable limit. The second distance is the distance between the centres of the two atoms. Although we believe that two water atoms at 2.4 A distance are too close, we only report water pairs that are closer than this rather short distance.

The last text-item on each line represents the status of the atom pair. If the final column contains the text 'HB', the bump criterion was relaxed because there could be a hydrogen bond. Similarly relaxed criteria are used for 1-3 and 1-4 interactions (listed as 'B2' and 'B3', respectively). BL indicates that the B-factors of the clashing atoms have a low B-factor thereby making this clash even more worrisome. INTRA and INTER indicate whether the clashes are between atoms in the same asymmetric unit, or atoms in symmetry related asymmetric units, respectively.

  65 VAL   ( 104-)  A      CG2 <->   66 ASN   ( 105-)  A      N      0.47    2.53  INTRA BF
 264 ALA   ( 304-)  A      O   <->  268 GLN   ( 308-)  A      CG     0.34    2.46  INTRA
 347 HIS   ( 387-)  A      ND1 <->  370 HIS   ( 410-)  A      ND1    0.34    2.66  INTRA BL
 182 ARG   ( 221-)  A      NH2 <->  597 HOH   (1013 )  A      O      0.33    2.37  INTRA BL
 257 ALA   ( 296-)  A      CB  <->  403 ASN   ( 445-)  A      ND2    0.32    2.78  INTRA
 121 GLN   ( 160-)  A      OE1 <->  303 LYS   ( 343-)  A      NZ     0.32    2.38  INTRA
 111 THR   ( 150-)  A      O   <->  149 LYS   ( 188-)  A      NZ     0.31    2.39  INTRA
 200 GLU   ( 239-)  A    A OE2 <->  597 HOH   (1041 )  A      O      0.29    2.11  INTRA
  66 ASN   ( 105-)  A      CA  <->   74 LYS   ( 113-)  A      NZ     0.28    2.82  INTRA BF
 308 ARG   ( 348-)  A      NH2 <->  597 HOH   (1118 )  A      O      0.22    2.48  INTRA
 385 LYS   ( 425-)  A      CE  <->  597 HOH   (1072 )  A      O      0.22    2.58  INTRA
  65 VAL   ( 104-)  A      O   <->   68 LEU   ( 107-)  A      N      0.21    2.49  INTRA BF
 465 ASP   ( 507-)  A      N   <->  466 PRO   ( 508-)  A      CD     0.20    2.80  INTRA BL
 278 GLU   ( 318-)  A      OE1 <->  342 HIS   ( 382-)  A      CE1    0.20    2.60  INTRA
  79 LYS   ( 118-)  A      NZ  <->  363 GLU   ( 403-)  A      OE2    0.19    2.51  INTRA
 592 ACT   ( 706-)  A      CH3 <->  597 HOH   (1196 )  A      O      0.19    2.61  INTRA BF
 201 LEU   ( 240-)  A      CD1 <->  486 ILE   ( 528-)  A      CD1    0.18    3.02  INTRA BL
 532 TRP   ( 574-)  A      N   <->  533 PRO   ( 575-)  A      CD     0.17    2.83  INTRA BL
 434 ILE   ( 476-)  A      CD1 <->  442 GLU   ( 484-)  A    A CG     0.15    3.05  INTRA
 386 HIS   ( 426-)  A      NE2 <->  597 HOH   (1110 )  A      O      0.15    2.55  INTRA
 294 GLU   ( 334-)  A      OE2 <->  298 LYS   ( 338-)  A      NZ     0.14    2.56  INTRA
 311 VAL   ( 351-)  A      O   <->  328 LYS   ( 368-)  A      NZ     0.13    2.57  INTRA BL
  65 VAL   ( 104-)  A      O   <->   68 LEU   ( 107-)  A      CB     0.13    2.67  INTRA BF
 349 GLN   ( 389-)  A      CG  <->  524 MET   ( 566-)  A      CE     0.13    3.07  INTRA
 239 MET   ( 278-)  A      N   <->  597 HOH   (1015 )  A      O      0.12    2.58  INTRA BL
And so on for a total of 82 lines.

Packing, accessibility and threading

Warning: Abnormal packing environment for some residues

The residues listed in the table below have an unusual packing environment.

The packing environment of the residues is compared with the average packing environment for all residues of the same type in good PDB files. A low packing score can indicate one of several things: Poor packing, misthreading of the sequence through the density, crystal contacts, contacts with a co-factor, or the residue is part of the active site. It is not uncommon to see a few of these, but in any case this requires further inspection of the residue.

 116 GLN   ( 155-)  A      -6.99
 461 GLN   ( 503-)  A      -6.14
 577 TYR   ( 619-)  A      -5.84
 219 HIS   ( 258-)  A      -5.72
 223 GLN   ( 262-)  A      -5.70
 571 LYS   ( 613-)  A      -5.57
  67 GLN   ( 106-)  A      -5.44
 227 LEU   ( 266-)  A      -5.16
 362 ARG   ( 402-)  A      -5.14
 451 GLN   ( 493-)  A      -5.14
 459 ARG   ( 501-)  A      -5.12

Warning: Abnormal packing environment for sequential residues

A stretch of at least three sequential residues with a questionable packing environment was found. This could indicate that these residues are part of a strange loop. It might also be an indication of misthreading in the density. However, it can also indicate that one or more residues in this stretch have other problems such as, for example, missing atoms, very weird angles or bond lengths, etc.

The table below lists the first and last residue in each stretch found, as well as the average residue score of the series.

 218 ARG   ( 257-)  A       220 - TYR    259- ( A)         -4.83

Warning: Low packing Z-score for some residues

The residues listed in the table below have an unusual packing environment according to the 2nd generation packing check. The score listed in the table is a packing normality Z-score: positive means better than average, negative means worse than average. Only residues scoring less than -2.50 are listed here. These are the unusual residues in the structure, so it will be interesting to take a special look at them.

  83 LEU   ( 122-)  A   -2.95
 542 GLN   ( 584-)  A   -2.60

Water, ion, and hydrogenbond related checks

Error: HIS, ASN, GLN side chain flips

Listed here are Histidine, Asparagine or Glutamine residues for which the orientation determined from hydrogen bonding analysis are different from the assignment given in the input. Either they could form energetically more favourable hydrogen bonds if the terminal group was rotated by 180 degrees, or there is no assignment in the input file (atom type 'A') but an assignment could be made. Be aware, though, that if the topology could not be determined for one or more ligands, then this option will make errors.

 116 GLN   ( 155-)  A
 388 HIS   ( 428-)  A

Warning: Buried unsatisfied hydrogen bond donors

The buried hydrogen bond donors listed in the table below have a hydrogen atom that is not involved in a hydrogen bond in the optimized hydrogen bond network.

Hydrogen bond donors that are buried inside the protein normally use all of their hydrogens to form hydrogen bonds within the protein. If there are any non hydrogen bonded buried hydrogen bond donors in the structure they will be listed here. In very good structures the number of listed atoms will tend to zero.

Waters are not listed by this option.

  66 ASN   ( 105-)  A      N
  97 ASN   ( 136-)  A      ND2
 125 ASP   ( 164-)  A      N
 136 TYR   ( 175-)  A      OH
 161 TYR   ( 200-)  A      OH
 176 ASP   ( 215-)  A      N
 226 ASN   ( 265-)  A      ND2
 234 HIS   ( 273-)  A      NE2
 238 ASN   ( 277-)  A      N
 243 THR   ( 282-)  A      N
 271 THR   ( 311-)  A      N
 316 ALA   ( 356-)  A      N
 325 PHE   ( 365-)  A      N
 326 ARG   ( 366-)  A      NH2
 347 HIS   ( 387-)  A      ND1
 362 ARG   ( 402-)  A      NH1
 366 ASN   ( 406-)  A      N
 399 GLU   ( 441-)  A      N
 400 HIS   ( 442-)  A    A N
 437 GLU   ( 479-)  A      N
 440 ASN   ( 482-)  A      N
 447 ARG   ( 489-)  A      NE
 457 VAL   ( 499-)  A      N
 478 TYR   ( 520-)  A      OH
 480 ARG   ( 522-)  A      N
 506 HIS   ( 548-)  A      NE2
Only metal coordination for  343 HIS  ( 383-) A      NE2
Only metal coordination for  347 HIS  ( 387-) A      NE2
Only metal coordination for  371 GLU  ( 411-) A      OE1

Warning: Buried unsatisfied hydrogen bond acceptors

The buried side-chain hydrogen bond acceptors listed in the table below are not involved in a hydrogen bond in the optimized hydrogen bond network.

Side-chain hydrogen bond acceptors buried inside the protein normally form hydrogen bonds within the protein. If there are any not hydrogen bonded in the optimized hydrogen bond network they will be listed here.

Waters are not listed by this option.

 263 GLU   ( 303-)  A      OE2
 278 GLU   ( 318-)  A      OE1
 329 GLN   ( 369-)  A      OE1
 342 HIS   ( 382-)  A      NE2
 344 GLU   ( 384-)  A      OE1
 344 GLU   ( 384-)  A      OE2

Warning: Possible wrong residue type

The residues listed in the table below have a weird environment that cannot be improved by rotamer flips. This can mean one of three things, non of which WHAT CHECK really can do much about. 1) The side chain has actually another rotamer than is present in the PDB file; 2) A counter ion is present in the structure but is not given in the PDB file; 3) The residue actually is another amino acid type. The annotation 'Alt-rotamer' indicates that WHAT CHECK thinks you might want to find an alternate rotamer for this residue. The annotation 'Sym-induced' indicates that WHAT CHECK believes that symmetry contacts might have something to do with the difficulties of this residue's side chain. Determination of these two annotations is difficult, so their absence is less meaningful than their presence. The annotation Ligand-bound indicates that a ligand seems involved with this residue. In nine of ten of these cases this indicates that the ligand is causing the weird situation rather than the residue.

 294 GLU   ( 334-)  A   H-bonding suggests Gln; but Alt-Rotamer
 431 ASP   ( 473-)  A   H-bonding suggests Asn; but Alt-Rotamer

Final summary

Note: Summary report for users of a structure

This is an overall summary of the quality of the structure as compared with current reliable structures. This summary is most useful for biologists seeking a good structure to use for modelling calculations.

The second part of the table mostly gives an impression of how well the model conforms to common refinement restraint values. The first part of the table shows a number of global quality indicators.


Structure Z-scores, positive is better than average:

  1st generation packing quality :  -0.089
  2nd generation packing quality :  -0.885
  Ramachandran plot appearance   :  -0.437
  chi-1/chi-2 rotamer normality  :  -1.775
  Backbone conformation          :  -0.083

RMS Z-scores, should be close to 1.0:
  Bond lengths                   :   0.522 (tight)
  Bond angles                    :   0.774
  Omega angle restraints         :   0.390 (tight)
  Side chain planarity           :   0.326 (tight)
  Improper dihedral distribution :   0.640
  B-factor distribution          :   0.610
  Inside/Outside distribution    :   0.995

Note: Summary report for depositors of a structure

This is an overall summary of the quality of the X-ray structure as compared with structures solved at similar resolutions. This summary can be useful for a crystallographer to see if the structure makes the best possible use of the data. Warning. This table works well for structures solved in the resolution range of the structures in the WHAT IF database, which is presently (summer 2008) mainly 1.1 - 1.3 Angstrom. The further the resolution of your file deviates from this range the more meaningless this table becomes.

The second part of the table mostly gives an impression of how well the model conforms to common refinement restraint values. The first part of the table shows a number of global quality indicators, which have been calibrated against structures of similar resolution.

Resolution found in PDB file : 2.18


Structure Z-scores, positive is better than average:

  1st generation packing quality :   0.5
  2nd generation packing quality :  -0.3
  Ramachandran plot appearance   :   0.7
  chi-1/chi-2 rotamer normality  :  -0.5
  Backbone conformation          :  -0.0

RMS Z-scores, should be close to 1.0:
  Bond lengths                   :   0.522 (tight)
  Bond angles                    :   0.774
  Omega angle restraints         :   0.390 (tight)
  Side chain planarity           :   0.326 (tight)
  Improper dihedral distribution :   0.640
  B-factor distribution          :   0.610
  Inside/Outside distribution    :   0.995
==============

WHAT IF
    G.Vriend,
      WHAT IF: a molecular modelling and drug design program,
    J. Mol. Graph. 8, 52--56 (1990).

WHAT_CHECK (verification routines from WHAT IF)
    R.W.W.Hooft, G.Vriend, C.Sander and E.E.Abola,
      Errors in protein structures
    Nature 381, 272 (1996).
    (see also http://swift.cmbi.ru.nl/gv/whatcheck for a course and extra inform

Bond lengths and angles, protein residues
    R.Engh and R.Huber,
      Accurate bond and angle parameters for X-ray protein structure
      refinement,
    Acta Crystallogr. A47, 392--400 (1991).

Bond lengths and angles, DNA/RNA
    G.Parkinson, J.Voitechovsky, L.Clowney, A.T.Bruenger and H.Berman,
      New parameters for the refinement of nucleic acid-containing structures
    Acta Crystallogr. D52, 57--64 (1996).

DSSP
    W.Kabsch and C.Sander,
      Dictionary of protein secondary structure: pattern
      recognition of hydrogen bond and geometrical features
    Biopolymers 22, 2577--2637 (1983).

Hydrogen bond networks
    R.W.W.Hooft, C.Sander and G.Vriend,
      Positioning hydrogen atoms by optimizing hydrogen bond networks in
      protein structures
    PROTEINS, 26, 363--376 (1996).

Matthews' Coefficient
    B.W.Matthews
      Solvent content of Protein Crystals
    J. Mol. Biol. 33, 491--497 (1968).

Protein side chain planarity
    R.W.W. Hooft, C. Sander and G. Vriend,
      Verification of protein structures: side-chain planarity
    J. Appl. Cryst. 29, 714--716 (1996).

Puckering parameters
    D.Cremer and J.A.Pople,
      A general definition of ring puckering coordinates
    J. Am. Chem. Soc. 97, 1354--1358 (1975).

Quality Control
    G.Vriend and C.Sander,
      Quality control of protein models: directional atomic
      contact analysis,
    J. Appl. Cryst. 26, 47--60 (1993).

Ramachandran plot
    G.N.Ramachandran, C.Ramakrishnan and V.Sasisekharan,
      Stereochemistry of Polypeptide Chain Conformations
    J. Mol. Biol. 7, 95--99 (1963).

Symmetry Checks
    R.W.W.Hooft, C.Sander and G.Vriend,
      Reconstruction of symmetry related molecules from protein
      data bank (PDB) files
    J. Appl. Cryst. 27, 1006--1009 (1994).

Ion Checks
    I.D.Brown and K.K.Wu,
      Empirical Parameters for Calculating Cation-Oxygen Bond Valences
    Acta Cryst. B32, 1957--1959 (1975).

    M.Nayal and E.Di Cera,
      Valence Screening of Water in Protein Crystals Reveals Potential Na+
      Binding Sites
    J.Mol.Biol. 256 228--234 (1996).

    P.Mueller, S.Koepke and G.M.Sheldrick,
      Is the bond-valence method able to identify metal atoms in protein
      structures?
    Acta Cryst. D 59 32--37 (2003).

Checking checks
    K.Wilson, C.Sander, R.W.W.Hooft, G.Vriend, et al.
      Who checks the checkers
    J.Mol.Biol. (1998) 276,417-436.