title: Distribution of low-density lipoprotein-bound low-molecular-weight thiols: a new analytical approach.
abstract: We have recently demonstrated that low-density lipoprotein (LDL) apoprotein is able to bind the most concentrated plasma thiols such as cysteine, cysteinylglycine, and homocysteine by disulfide linkage. However, the LIF CE assay employed to measure linked thiols was not sensitive enough to verify whether low concentrated plasma thiols as glutathione and glutamylcysteine are also linked to apoprotein. By modifying sample treatment and electrophoretic parameters we set up a new method with an LOQ of about 1.5 nmol/L, by which we demonstrate that LDL apoprotein binds all physiological plasma thiols. The increased sensitivity was obtained by drying released apoB thiols after reduction treatment, dissolving them directly in a low volume of derivatization buffer and decreasing the dilution factor of derivatized sample before CE injection. Moreover, by increasing the concentration of the electrolyte buffer, we improved the selectivity of peaks, in particular between glutathione (GSH) and the impurity peak derived from unreacted 5-iodoacetamidofluorescein, which in the previous electrophoretic conditions were overlapped. The method optimization, reached by searching the best combination between sample matrix and CE run buffer, is fully described. Given the potential pathologic significance of protein thiolation, the proposed method may be useful to understand the mechanisms and the balances that regulate the interaction between thiols and -SH free groups of proteins.
authors.affiliation: Dipartimento di Scienze Biomediche, Cattedra di Biochimica Clinica, Università di Sassari, Italy. angelozinellu@libero.it
authors.forename: Angelo
authors.initials: A
authors.lastname: Zinellu
authors.forename: Salvatore
authors.initials: S
authors.lastname: Sotgia
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Zinellu
authors.forename: Marilena
authors.initials: M
authors.lastname: Formato
authors.forename: Salvatorica
authors.initials: S
authors.lastname: Manca
authors.forename: Stefania
authors.initials: S
authors.lastname: Magliona
authors.forename: Renzo
authors.initials: R
authors.lastname: Ginanneschi
authors.forename: Luca
authors.initials: L
authors.lastname: Deiana
authors.forename: Ciriaco
authors.initials: C
authors.lastname: Carru
mesh_terms: D001055:Apolipoproteins B / Q000097:blood* / Q000378:metabolism; D019075:Electrophoresis, Capillary / Q000379:methods*; D006801:Humans; D008077:Lipoproteins, LDL / Q000097:blood* / Q000378:metabolism; D008970:Molecular Weight; D013438:Sulfhydryl Compounds / Q000097:blood* / Q000378:metabolism
chemical_list: D001055:Apolipoproteins B; D008077:Lipoproteins, LDL; D013438:Sulfhydryl Compounds