Graphene oxide as a protein matrix: influence on protein biophysical properties

Abstract

BackgroundThis study provides fundamental information on the influence of graphene oxide (GO) nanosheets and glycans on protein catalytic activity, dynamics, and thermal stability. We provide evidence of protein stabilization by glycans and how this strategy could be implemented when GO nanosheets is used as protein immobilization matrix. A series of bioconjugates was constructed using two different strategies: adsorbing or covalently attaching native and glycosylated bilirubin oxidase (BOD) to GO.ResultsBioconjugate formation was followed by FT-IR, zeta-potential, and X-ray photoelectron spectroscopy measurements. Enzyme kinetic parameters (km and kcat) revealed that the substrate binding affinity was not affected by glycosylation and immobilization on GO, but the rate of enzyme catalysis was reduced. Structural analysis by circular dichroism showed that glycosylation did not affect the tertiary or the secondary structure of BOD. However, GO produced slight changes in the secondary structure. To shed light into the biophysical consequence of protein glycosylation and protein immobilization on GO nanosheets, we studied structural protein dynamical changes by FT-IR H/D exchange and thermal inactivation.ConclusionsIt was found that glycosylation caused a reduction in structural dynamics that resulted in an increase in thermostability and a decrease in the catalytic activity for both, glycoconjugate and immobilized enzyme. These results establish the usefulness of chemical glycosylation to modulate protein structural dynamics and stability to develop a more stable GO-protein matrix.Electronic supplementary materialThe online version of this article (doi:10.1186/s12951-015-0134-0) contains supplementary material, which is available to authorized users.

Immobilization of formate dehydrogenase on polyethylenimine‐grafted graphene oxide with kinetics and stability study

“…The interaction with GO induced a structural transformation from -helix to -sheet, even to the unfolding of the glucose oxidase, which resulted in the main loss of enzyme activity [24]. Similar phenomenon was found in brilirulin oxidase, horseradish peroxidase, catalase, cytochrome c, and esterase [25][26][27][28][29]. The relation between the alteration of catalytic properties and structure transformation merits further investigation.…”

The Synergy of Graphene Oxide and Polydopamine Assisted Immobilization of Lysozyme to Improve Antibacterial Properties

“…This phenomenon was attributed to the fact that cLY was fixed on the PDA/rGO film mainly through electrostatic adsorption. Hence, the bioconjugates of PDA/rGO‐cLY was formed both by physical adsorption and hydrogen bond interaction …”

“…Hence, the bioconjugates of PDA/rGO-cLY was formed both by physical adsorption and hydrogen bond interaction. [28,29] The zeta-potential can also provide additional evidence of the formation of the PDA/rGO-cLY bioconjugates ( Table S1). GO in 0.1 M PBS pH 7.4 solution showed a zeta-potential of À 23 AE 1 mV in agreement with previously reported potentials atp H 7.…”

“…It is widely exposure that PDA‐coating surface can improve the stabilization of nanoparticles, enzymes and other materials . In especial, some reports confirm the activity and stability of protein are better after immobilized via covalently bond, physical adsorption and hydrogen bond interaction . Yuhong Renet al have revealed that with immobilized on PD‐MNPs, pH and thermal stability of lipase have been enhanced compared to free lipase .…”

“…[26] In especial, some reports confirm the activity and stability of protein are better after immobilized via covalently bond, physical adsorption and hydrogen bond interaction. [27][28][29] Yuhong Renet al have revealed that with immobilized on PD-MNPs, pH and thermal stability of lipase have been enhanced compared to free lipase. [24] David M. Donovan and Shai Rahimipour et al have exhibited that immobilization of recombinantly produced lysostaphin onto PDA-coated surfaces can be carried out under physiological conditions.…”