Guncheva M.Raynova Y.Idakieva K.Todinova S.Yancheva D.2024-07-162024-07-162024-07-162024-07-162020-01-011314-79781314-7471SCOPUS_ID:85129276447https://rlib.uctm.edu/handle/123456789/1379This is the first report on the synthesis of vitamin B9-Rapana thomasiana hemocyanin conjugates (vit. B9-RtH). Proteins modified with 25 and 150 vitamin B9 residues аre obtained in a coupling reaction between N-hydroxysuccinimide-activated γ -carboxylic groups of vitamin B9 and the amino-groups of N-terminal amino acids and lysines comprising the protein. ATR-FTIR spectroscopy is applied to monitor the changes of the secondary structure upon the modification. The comparison of the secondary structure of the native and the vitamin B9-conjugated RtHs shows that the modification results in an increase of the β-structures in a favor of α-helices and coiled structures. The therrmal stability of the novel preparations is evaluated by differential scanning calorimetry (DSC). Despite the serious changes of the conformation, the vit.-B9-RtH conjugates are characterized by a high thermal stability. It is assumed that the changes of the DSC profiles are due to alternative protein-protein interactions, e.g H-bonding, stacking or hydrophobic interactions with vitamin B9 moieties that are possible in the modified RtH moleculesenArticle