Bioencapsulation of apomyoglobin in nanoporous organosilica sol–gel glasses: Influence of the siloxane network on the conformation and stability of a model protein |
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| Authors: | Bouzid Menaa Yuya Miyagawa Masahide Takahashi Mar Herrero Vicente Rives Farid Menaa Daryl K Eggers |
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| Institution: | 1. Department of Chemistry, Duncan Hall, San José State University, San José, CA 95112‐0101;2. Fluorotronics, Inc., 3350 General Atomics Court, Building #2, General Atomics Science Industrial Center, San Diego, CA 92121;3. Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611‐0011, Japan;4. GIR‐QUESCAT‐Departamento de Química Inorgánica, Universidad de Salamanca, 37008 Salamanca, Spain |
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| Abstract: | Nanoporous sol–gel glasses were used as host materials for the encapsulation of apomyoglobin, a model protein employed to probe in a rational manner the important factors that influence the protein conformation and stability in silica‐based materials. The transparent glasses were prepared from tetramethoxysilane (TMOS) and modified with a series of mono‐, di‐ and tri‐substituted alkoxysilanes, RnSi(OCH3)4?n (R = methyl‐, n = 1; 2; 3) of different molar content (5, 10, 15%) to obtain the decrease of the siloxane linkage (? Si? O? Si? ). The conformation and thermal stability of apomyoglobin characterized by circular dichroism spectroscopy (CD) was related to the structure of the silica host matrix characterized by 29Si MAS NMR and N2 adsorption. We observed that the protein transits from an unfolded state in unmodified glass (TMOS) to a native‐like helical state in the organically modified glasses, but also that the secondary structure of the protein was enhanced by the decrease of the siloxane network with the methyl modification (n = 0 < n = 1 < n = 2 < n = 3; 0 < 5 < 10 < 15 mol %). In 15% trimethyl‐modified glass, the protein even reached a maximum molar helicity (?24,000 deg. cm2 mol?1) comparable to the stable folded heme‐bound holoprotein in solution. The protein conformation and stability induced by the change of its microlocal environment (surface hydration, crowding effects, microstructure of the host matrix) were discussed owing to this trend dependency. These results can have an important impact for the design of new efficient biomaterials (sensors or implanted devices) in which properly folded protein is necessary. © 2009 Wiley Periodicals, Inc. Biopolymers 91: 895–906, 2009. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com |
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| Keywords: | sol– gel glasses bio‐encapsulation siloxane network protein‐silica interactions protein folding circular dichroism spectroscopy |
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