Mean density of proteins in the crystalline form

Range ~1.22 g/cm^3
Organism Generic
Reference Andersson KM, Hovmöller S. The protein content in crystals and packing coefficients in different space groups. Acta Crystallogr D Biol Crystallogr. 2000 Jul56(Pt 7):789-90. Doi: 10.1107/S0907444900005163 link abstract, p.789 left column top paragraph & p.790 middle column 3rd paragraph PubMed ID10930824
Primary Source Andersson, K. M. & Hovmöller, S. (1998). The average atomic volume and density of proteins. Z. Kristallogr. 213, 369-373. DOI: 10.1524/zkri.1998.213.7-8.369 link
Method Abstract: "A precise way of estimating the packing coefficient, i.e. the ratio between the protein and unit-cell volume, or solvent content in protein crystals is given. At present, the solvent content is not given for most proteins in the Protein Data Bank and in many cases where it is given the values are dubious."
Comments Abstract: "The mean density of proteins in the crystalline form is around 1.22 g/cm^3, not 1.35 g/cm^3 as usually stated. This is equivalent to 19.5 A^3 per non-H atom." P.789 left column top paragraph: "The packing coefficient of organic molecular crystals is often in the range 65-77% (Kitai-gorodskii, 1973). However, in protein crystals the packing coefficient (1-solvent fraction) is lower. Crick & Kendrew (1968) gave an estimate of 40-60%. This estimate was based on the assumption that proteins have a density of 1.35 g/cm^3. Given a revised value for the protein density of 1.22 g/cm^3 (primary source), the protein volume and hence the packing coefficient will be larger." P.790 middle column 3rd paragraph: "In the PDB [Protein Data Bank], solvent content is given for less than half of all entries and for only 71 of the 181 proteins studied here. In most cases, the solvent is overestimated by about 10% (for instance 50% when 45% is more correct, but there are considerable variations). This discrepancy follows from the different density values used for protein crystals i.e. 1.35 g/cm^3 instead of 1.22 g/cm^3."
Entered by Uri M
ID 112767