Biodegradable, biocompatible nanoparticles with tuneable fluorescence - due to their great potential in biology, medicine and sensor development - are widely studied nowadays. Recently it was shown that the complex red emitting spectroscopic feature of Bovine Serum Albumin - gold (BSA[sbnd]Au) bioconjugates can be related to the versatility of conformational changes of the BSA protein. In our study, we performed a comprehensive study on the structural changes of the host BSA molecules by infrared spectroscopy (FTIR) and small-angle X-ray scattering (SAXS). Both methods revealed that the BSA structure is not reversible after a neutral - alkali - neutral pH cycle and this behaviour is more pronounced in the presence of the gold salt (HAuCl4). The changes in the monitored secondary structural elements of BSA-(HAuCl4) system, with the fitted molecular shapes indicate that all steps in the synthesis route influence both the fine and the global structures of BSA and result in a complex structural prehistory dependent hindering of the total structural reversibility. A robust connection exists between the structural/conformational changes and the fluorescence behaviours.
Bibliographical noteFunding Information:
This work was completed in the ELTE Thematic Excellence Programme (Synthesis+) supported by the Hungarian Ministry for Innovation and Technology as well as in the ELTE Institutional Excellence Programme supported by the National Research, Development and Innovation Office (NKFIH-1157-8/g2019-DT). Project no. 2018-1.2.1-NKP-2018-00005 has also been implemented with the support provided from the National Research, Development and Innovation Fund of Hungary, financed under the 2018-1.2.1-NKP funding scheme. This publication was produced under the operation program called Research and Innovation for the project: ?Support of research and development capacities in the area of nanochemical and supramolecular systems?, code ITMS2014+ 313011T583, funded from the resources of the European Regional Development Fund. Support from Independent Research Fund Denmark (Natural Sciences, grant no 4002-00479 and grant no 8021-00133B) and Independent Research Fund Denmark (Technology and Production, grant no 4184-00218) are gratefully acknowledged for funding.