muramidase and azobenzene

Exploring the interaction between an azobenzene-based photoswitch and natural protein can help elucidate how the photo-control of an optical molecule participates in the transmission and delivery of proteins, as well as the effects of azo-switch trans and cis states on protein configurations. In this study, fluorescence analysis, circular dichroism spectroscopy, molecular docking, and molecular dynamics simulations were used to study the interaction among different configurations of tetra-ortho-methoxy substituted azobenzene di-maleimide (toM-ABDM), a red light-induced optical azo-switch, and lysozyme (LYZ). Results showed that toM-ABDM caused the static quenching of LYZ. The cis toM-ABDM had stronger binding affinity than trans toM-ABDM. The noncovalent interaction, hydrogen bonds and van der Waals forces, could not regulate the conformation of LYZ in photo-control. A binding model of toM-ABDM and LYZ in different forms induced by red and blue light was further established by computer simulation.

Topics: Animals; Azo Compounds; Chickens; Isomerism; Kinetics; Light; Molecular Conformation; Molecular Docking Simulation; Molecular Dynamics Simulation; Muramidase; Spectrometry, Fluorescence; Thermodynamics

The capability of the photoresponsive isomerization of azobenzene derivatives in self-assembled monolayer (SAM) surfaces to control protein adsorption behavior has very promising applications in antifouling materials and biotechnology. In this study, we performed an atomistic molecular dynamics (MD) simulation in combination with free-energy calculations to study the morphology of azobenzene-terminated SAMs (Azo-SAMs) grafted on a silica substrate and their interactions with lysozyme. Results show that the Azo-SAM surface morphology and the terminal benzene rings' packing are highly correlated with the surface density and the isomer state. Higher surface coverage and the trans-isomer state lead to a more ordered polycrystalline backbone as well as more ordered local packing of benzene rings. On the Azo-SAM surface, water retains a high interfacial diffusivity, whereas the adsorbed lysozyme is found to have extremely low mobility but a relative stable secondary structure. The moderate desorption free energy (∼60 kT) from the trans-Azo-SAM surface was estimated by using both the nonequilibrium-theorem-based Jarzynski's equality and equilibrium umbrella sampling.

Topics: Adsorption; Azo Compounds; Diffusion; Models, Molecular; Muramidase; Particle Size; Silicon Dioxide; Surface Properties; Water

On the basis of the host-guest interactions between azobenzenes and cyclodextrins, a new strategy for the preparation of a dually functionalized poly(dimethylsiloxane) (PDMS) surface was investigated using surface-initiated atom-transfer radical polymerization (SI-ATRP) and click chemistry. The PDMS substrates were first oxidized in a H(2)SO(4)/H(2)O(2) solution to transform the surface Si-CH(3) groups into Si-OH groups. Then, the SI-ATRP initiator 3-(2-bromoisobutyramido)propyl(trime-thoxy)silane was grafted onto the substrates through a silanization reaction. Sequentially, the poly(ethylene glycol) (PEG) units were introduced onto the PDMS-Br surfaces via SI-ATRP reaction using oligo(ethylene glycol) methacrylate. Afterward, the bromide groups on the surface were converted to azido groups via nucleophilic substitution reaction with NaN(3). Finally, the azido-grafted PDMS surfaces were subjected to a click reaction with alkynyl and PEG-modified β-cyclodextrins, resulting in the grafting of cyclodextrins onto the PDMS surfaces. The composition and chemical state of the modified surfaces were characterized via X-ray photoelectron spectroscopy, and the stability and dynamic characteristics of the cyclodextrin-modified PDMS substrates were investigated via attenuated total reflection-Fourier transform infrared spectroscopy and temporal contact angle experiments. The surface morphology of the modified PDMS surfaces was characterized through imaging using a multimode atomic force microscope. A protein adsorption assay using Alexa Fluor594-labeled bovine serum albumin, Alexa Fluor594-labeled chicken egg albumin, and FITC-labeled lysozyme shows that the prepared PDMS surfaces possess good protein-repelling properties. On-surface studies on the interactions between azobenzenes and the cyclodextrin-modified surfaces reveal that the reversible binding of azobenzene to the cyclodextrin-modified PDMS surfaces and its subsequent release can be reversibly controlled using UV irradiation. Sandwich fluoroimmunoassay of the cardiac markers myoglobin and fatty acid-binding protein demonstrates that the cyclodextrin-modified PDMS surfaces can be repeatedly utilized in disease biomarker analysis.

Topics: Animals; Azo Compounds; beta-Cyclodextrins; Biomarkers; Cardiovascular Diseases; Cattle; Dimethylpolysiloxanes; Fatty Acid-Binding Proteins; Fluoroimmunoassay; Humans; Muramidase; Myoglobin; Organic Chemicals; Photoelectron Spectroscopy; Polyethylene Glycols; Serum Albumin, Bovine; Surface Properties

The interaction of a light-responsive surfactant with lysozyme at pH 5.0 has been investigated as a means to control protein structure and enzymatic activity with light illumination. The cationic azobenzene surfactant undergoes a reversible photoisomerization upon exposure to the appropriate wavelength of light, with the visible-light (trans) form being more hydrophobic and, thus, inducing a greater degree of protein unfolding than the UV-light (cis) form. Conformational changes as a function of photoresponsive surfactant concentration and light illumination were measured through shape-reconstruction analysis of small-angle neutron scattering (SANS) data. The SANS-based in vitro structures indicate that lysozyme transitions from a nativelike structure at low surfactant concentration to a partially unfolded conformation at higher surfactant concentrations under visible light illumination, while UV-light illumination causes the protein to refold to a near-native structure. Protein swelling occurs principally away from the active site near the hinge region connecting the alpha and beta domains, leading to an increase in the observed separation distance of the alpha and beta domains in the ensemble SANS measurements, a likely result of enhanced domain motions and increased flexibility within the protein. This swelling of the hinge region is accompanied by an 8-fold increase in enzymatic activity relative to the native state. Both enzyme swelling and superactivity observed under visible light can be reversed to nativelike conditions upon exposure to UV light, leading to complete photoreversible control of the structure and function of lysozyme.

Topics: Animals; Azo Compounds; Chitin; Enzyme Activation; Hydrogen-Ion Concentration; Light; Molecular Structure; Muramidase; Photochemistry; Protein Conformation; Surface-Active Agents; Ultraviolet Rays