Question

3. (20 pts) The tripeptide glutathione, GSH, which is a major component in the cell, has the structure and pKa values shown below. Answer the following. a. By considering only the cysteine residue of GSH, determine the concentration of the thiol form of GSH if the total concentration of GSH in the cytosol is 2.00 mM and the pH of the cytosol is pH = 7.4. b. Glutathione is considered a polyfunctional ligand. Which donor atoms of GSH would likely form the most stable bidentate chelate with Mnat pH - 10? Using basic structural and bonding concepts in coordination chemistry, briefly give the reasons for your choice. O HH2 H2HH H2N -C-C -C -C-N- C. (9.65) COH CH2 (2.12) (8.75) SH -N-C-CO,H (3.59)

Answer 1

From Hendexs on - Hasselbalch canation we get PH= pk at de Cop) ....) here, p- protonated form. OP= de protonated form. pka – log ka, ka=Eanilithium constant for acid form pH = -log[it) now from canation () we get, dagen pu - pka pH-pka tupka ... (in) when, pH7Pka then Copy to PHpka then COPK (P] then tools [P] PH=pka a phares here, zu 44 ICH & anod : Thiol form of GSH ole propotonated Protonated form DP form ,p GSH in the cytosol in 2.00mm & o.anim then [P]+ EDP] = 0.002... (ii) von from canation (in we get, [Op . 7.4 - 8.75 CM - 70 71% - 875 - 0.045 .: lop) - 0.045 (P) = 0.00- (P) = 0.004ste turung sinh :-) .002 = 045 () & (P)- 0.002 /1.004s - 0 colgam = 1.980 m : Cp). 0.045 - 00199 M = 8.9x20 mm Concentration of this form . - 1.99x10? - 1.99 mm ( 10m Irm 1

12 PH10 is greater than all the pka valuer of 6 St. So, all finectional group remain derpronated. here, -Coot of d-glu & - SH of lage auill be anionic form of they are close Ewximity. So, with these are ion most stable bidentale che la te auill be formed auth wont at PH 10 at PH10 the GS44 min2t interaction. H₂N- & _ 2 – 2 – E-B-u – 200 coo- un ingeren's checate formation