The AuNPs prepared with PBHs containing Met residue were stabilised with a lower Tipifarnib number of ligands on each AuNP surface compared to the AuNPs capped with other PBH ligands. A direct comparison of Au[(Met)2B] and Au[(TrCys)2B] revealed fewer ligands for the Met-containing PBH-AuNP, despite both having the same diameter. 1H NMR spectra and FT-IR absorption spectra of free PBHs and of the PBH-capped AuNPs were measured to identify the interactions between the gold

surface and the capping ligand. The NMR spectra of the AuNPs showed broad signals click here compared to the free PBHs. Figure 3 shows 1H NMR spectra of Au[(Gly-Tyr-Met)2B] and its free PBH (Gly-Tyr-Met)2B in DMSO-d 6. The signal of the H-α of the Met residue appeared at approximately 1.5 ppm in the PBH (Gly-Tyr-Met)2B NMR spectrum and was significantly broadened in that

of Au[(Gly-Tyr-Met)2B]. A similar line broadening was also observed in the NMR spectrum of Au[(Gly-Trp-Met)2B] (Figure 3) and of Au[(Met)2B] (see Additional file 2: Figure S1). These observations indicate that the PBH was attached to the gold surface through the Met residue [46]. Analogous results were observed for the NMR spectra of Au[(Gly-Tyr-TrCys)2B] and Au[(TrCys)2B] [9], where the sulphur atom of the TrCys residue is https://www.selleckchem.com/products/dibutyryl-camp-bucladesine.html involved in the surface binding. Figure 3 1 H NMR spectra of 4-Aminobutyrate aminotransferase free PBHs and PBH-capped AuNPs. (a) Free PBH (Gly-Tyr-Met)2B (top) and 1H NMR spectrum of AuNP Au[(Gly-Tyr-Met)2B] (bottom) in DMSO-d6, and (b) 1H NMR spectrum of free PBH (Gly-Trp-Met)2B (top)

and 1H NMR spectrum of AuNP Au[(Gly-Trp-Met)2B] (bottom) in DMSO-d6. Table 1 Structural characteristics of the AuNPs from elemental analysis and TEM data AuNP Size (nm) Calculated m/na from %Nb Number of Au atomsc PBH units per Au nanoparticle Mw Au[(Gly-Trp-Met)2B] 1.6 0.062 126 8 32,106 Au[(Gly-Tyr-TrCys) 2 B] 1.8 0.22 180 40 90,397 Au[(Gly-Tyr-Met)2B] 1.5 0.064 104 7 27,100 Au[(Met)2B] 2.3 0.154 375 57 102,625 Au[(TrCys)2B] 2.3 0.26 375 97 164,377 Bold emphasis is used to signal the most stable AuNP; a m, Number of PBH units; n, Number of Au atoms; b%N from elemental analysis; cestimated supposing spherical particles and applying N = 30.89602 D3 [47]. The FT-IR spectra are shown in Figure 4. For Au[(Gly-Tyr-Met)2B], Au[(Gly-Trp-Met)2B] and Au[(Met)2B], the band caused by the C = O stretching mode of the carboxylic group was absent. However, two bands were observed around 1,600 and 1,398 cm−1, assigned to the asymmetric and symmetric stretching vibrations of carboxylate anions [48]. These results suggest that the carboxylic groups are also involved in PBH interactions with the gold surface. Significant changes were observed in the amide I band in the spectra of capped NPs compared with those of the free PBHs.