Re: [ccp4bb] Regarding difference in ITC and structure data

[Boaz Shaanan]

Hi, Just to emphasize Philippe's statement: binding carbohydrates by proteins (lectins or other types) is often, if not exclusively, an entropy driven process. Hence, the low enthalpy contribution that you observe may be real. Maybe. My 2p thoughts. Stay safe. Boaz     Boaz Shaanan, Ph.D.                                         Dept. of Life Sciences                                      Ben-Gurion University of the Negev                          Beer-Sheva 84105                                            Israel                                                                                                                  E-mail: bshaa...@bgu.ac.il Phone: 972-8-647-2220                     Fax:   972-8-647-2992 or 972-8-646-1710                          From: CCP4 bulletin board <CCP4BB@JISCMAIL.AC.UK> on behalf of DUMAS Philippe (IGBMC) <p.du...@ibmc-cnrs.unistra.fr> Sent: Saturday, August 1, 2020 11:42 AM To: CCP4BB@JISCMAIL.AC.UK Subject: Re: [ccp4bb] Regarding difference in ITC and structure data   Monika Did you try ITC experiments at different temperatures ? Delta H may be null, or close to zero, at some temperature without implying that there is no binding ! Philippe Dumas De: "monika chandravanshi" <chandravanshi.monik...@gmail.com> À: "CCP4BB" <CCP4BB@JISCMAIL.AC.UK> Envoyé: Samedi 1 Août 2020 09:57:24 Objet: [ccp4bb] Regarding difference in ITC and structure data Dear All, I am working on a carbohydrate-binding protein, which co-crystallizes with maltose, maltotriose, maltotetraose and maltopentaose and the same can be supported by ITC experiments as well. Also, the mutant protein (X2Y) co-crystallizes with maltose, maltotriose, maltotetraose and maltopentaose, however, the binding of only maltotriose and maltotetraose could be observed through ITC. For your information, the ITC conditions are the same for all the ligands and the ligand concentration used in ITC is same as used in crystallization (100x of protein concentrations). Moreover, from structural analysis, we have observed that the binding mode of all ligands is the same.  I request your suggestion on why maltose and maltopentaose do not show any binding to the mutant protein in ITC experiments. Looking forward to suggestions. Best Regards, Monika  To unsubscribe from the CCP4BB list, click the following link: https://www.jiscmail.ac.uk/cgi-bin/WA-JISC.exe?SUBED1=CCP4BB&A=1 To unsubscribe from the CCP4BB list, click the following link: https://www.jiscmail.ac.uk/cgi-bin/WA-JISC.exe?SUBED1=CCP4BB&A=1 To unsubscribe from the CCP4BB list, click the following link: https://www.jiscmail.ac.uk/cgi-bin/WA-JISC.exe?SUBED1=CCP4BB&A=1