Half sphere exposure used in predicting discontinuous B-cell epitopes. Song et al. have developed an online webserver termed HSEpred to predict half-sphere exposure from protein primary sequences. HSEpred server can achieve the correlation coefficients of 0.72 and 0.68 between the predicted and observed HSE-up and HSE-down measures, respectively, when evaluated on a well-prepared non-homologous protein structure dataset. Moreover, residue contact number (CN) can also be accurately predicted by HSEpred webserver using the summation of the predicted HSE-up and HSE-down values, which has further enlarged the application of this new solvent exposure measure. Recently, Heffernan et al. has developed the most accurate predictor for
Ewald's sphere falling on the crystal has a wave vector formula_2 whose length is formula_3. The diffracted plane wave has a wave vector formula_4. If no energy is gained or lost in the diffraction process (it is elastic) then formula_4 has the same length as formula_2. The difference between the wave-vectors of diffracted and incident wave is defined as scattering vector formula_7. Since formula_2 and formula_4 have the same length the scattering vector must lie on the surface of a sphere of radius formula_3. This sphere is called the Ewald sphere. The reciprocal lattice points are the values of momentum transfer where