Coordination and Photoisomerization of Azobenzene-Amino Acid Schiff Base Copper(II) Complexes to Lysozyme

Abstract

In this study, we exhibited an amino acid (arginine and threonine) derivative Schiff base copper(II) complexes incorporating an azobenzene moiety as a photoresponsive site and conjugated it to egg white lysozyme, a well-known protein, to change ligand conformation under binding to lysozyme. Among several spectroscopic investigations, ESR clearly showed that the nitrogen atom of the amino acid residue of lysozyme was bound to the paramagnetic copper(II) ion of the complex, and UV light irradiation confirmed photoisomerization of the azobenzene moiety of the ligand to cis-form. The binding mode was considered by means of spectroscopic as well as computational methods, whereas complete crystallographic verification was still a preliminary stage.

Inversely Finding Peculiar Reaction Conditions toward Microfluidic Droplet Synthesis

“…However, aside from the MEMS (micro-electromechanical systems) technology, which is a methodology, a reaction theory that considers the reaction system and spatial factors and clearly shows their effects has not been established regarding the base chemistry. Papers that serve as conventional methods and technologies have already been published [2], and there is also an accumulation of negative data. In particular, in recent years, the author and his colleagues have established the synthesis conditions [29] and calculation results [30] for amino-acid-Schiff-base-metal complexes in order to apply them to microwave synthesis [31] (the realization of spatial and electromagnetic temperature distribution) and microfluidic device synthesis (the realization of nanoscale-specific kinetics and thermodynamics).…”

“…conventional methods and technologies have already been published [2], and there is also an accumulation of negative data. In particular, in recent years, the author and his colleagues have established the synthesis conditions [29] and calculation results [30] for amino-acid-Schiff-base-metal complexes in order to apply them to microwave synthesis [31] (the realization of spatial and electromagnetic temperature distribution) and microfluidic device synthesis (the realization of nanoscale-specific kinetics and thermodynamics).…”

“…The author would like to create protein crystals containing metal complexes with aldehydes with hydrophobic moieties, such as photo-functionality (azobenzene) and Schiff bases, which are N-terminal-condensed water-soluble proteins, such as lysozyme, as ligands, which are usually difficult, and to stably synthesize useful multi-functional materials, such as SOD-active-metal complex catalysts (artificial metalloproteins), that work in watersoluble environments [1,2]. Therefore, the purpose of the hypothesis of this research is to obtain knowledge that will be useful in the future for "conditions for accelerating the droplet reaction of complex-containing protein crystals" by taking into account the accumulation and discussion of negative data "due to the inverse scale effect", aiming to make a contribution to the establishment of elemental technology for droplet synthesis in microfluidic devices (discovering the reactions and processes in which the scale effect is effective).…”

Mathematical Geometry and Groups for Low-Symmetry Metal Complex Systems

“…We can proceed further to low-symmetry systems taken from our studies. For example, we studied a copper(II) complex incorporating L-amino acid derivatives, known as Schiff base [23] (Figure 1). Its coordination geometry deviates from the regular square planar one and the tetrahedral one.…”

“…The coordination bond angles in cis-positions are between about 85 and 97 degrees, which suggests that it affords a distorted square planar geometry (deviating from regular D4h symmetry). In an experimental study [23], electronic spectra were discussed mainly for the photoisomerization of the azobenzene moiety of a ligand (focused on π−π* bands), and infrared spectra were used only for the purpose of characterization. Thus, the assignment of a d-d transition based on electronic (or circular dichroism) spectroscopy, as well as vibrational normal modes (if a more complex discussion is needed), should be carried out using the results of computational chemistry, such as density functional theory calculations after As for molecular symmetry, "Molecules without an axis of reflection (rotational axis) S n are chiral."…”