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Hi Kavya, My guess is that you are referring to the van der Waals (vdw) contribution of the hydrophobic effect (the other being of entropic nature). If this is the case, then the most reasonable consensus is that Dij < Ri + Rj + 2 R(H2O), where Dij is the distance between atoms i and j, Ri is the vdw radius of atom i, Rj, the vdw radius of atom j and R(H2O) the vdw radius of the water molecule. Doing so, you state that as far as two atoms are close enough to avoid being solvated (either one!), then they are close enough to engage in vdw interaction and if the atoms being considered are both nonpolar, that would correspond to what you call hydrophobic "interaction". Therefore, the distances that you state are likely meaningless, depending on the sizes of the atoms concerned. I suppose you are using unified atoms; in which case, e.g., CH2 is about 1.8 Ang. If you take R(H2O) = 1.4 Ang, then 1.8 + 1.8 + 2x1.4 = 5.0 Ang. 8 Ang is far too much for CH2/CH2! HTH, Nadir Mrabet Pr. Nadir T. Mrabet Structural & Molecular Biochemistry N-gere - INSERM U-954 University of Lorraine, Nancy School of Sciences and Technologies & School of Medicine 9, Avenue de la Foret de Haye, BP 184 54505 Vandoeuvre-les-Nancy Cedex France Phone: +33 (0)3.83.68.32.73 Fax: +33 (0)3.83.68.32.79 E-mail: Nadir.Mrabet <at> univ-lorraine.fr LEGAL NOTICE Unless expressly stated otherwise, this message is confidential and may be privileged. It is intended for the addressee(s) only. Access to this E-mail by anyone else is unauthorized. If you are not an addressee, any disclosure or copying of the contents of this E-mail, or any action taken (or not taken) in reliance on it, is unauthorized and may be unlawful. If you are not an addressee, please inform the sender immediately. ----- Mail original ----- Dear users, Sorry for an off-topic question. What is the limits for hydrophobic interactions in protein? Some prefer 5Ang some prefer upto 8Ang. Any reference or suggestions are welcome. Thanking you Regards Kavya -- This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean.