Study on the Long Lifetime of the M State in Chemically Modified Bacteriorhodopsin Film

Abstract

The M-state lifetime of bacteriorhodopsin (BR) could be significantly prolonged by using diaza-15-crown-5 as a chemical additive in BR−PVA films. With increasing additive content, the decay of the M-state was slowed gradually. At the highest BR/diaza-15-crown-5 molecular ratio of 1:250, the lifetime of the M state (τ1/e) could be prolonged to 568 s, which represents over a 4-order-of-magnitude improvement on the 10-ms lifetime of the native BR protein.

Amphiphilic block copolymers significantly influence functions of bacteriorhodopsin in water

“…Usually, a long lifetime of the M intermediate can be achieved in dehydrated BR 57 and dried BR-polymer composite films. 58,59 In the present study, BR-P123 assemblies collected by centrifugation of the PM treated in 5 wt% P123 were embedded into the PVA films. The kinetic traces of the flash-induced M intermediate of BR-P123 assemblies in solution and in a dried PVA film are shown in Fig.…”

“…36,37,40 According to the previous literature, a long lifetime of the M intermediate of BR can be obtained by appropriate mutation, 33 addition of some chemicals like lanthanum ions 75 and guanidine hydrochloride 76 and in dried BR or in dry BR-polymer films. [57][58][59] In this paper, we have, by addition of amphiphilic polymers, achieved a significant prolongation of the M decay of BR in solution, of the same order of that in a dry BR-polymer film, which is significantly longer when compared with that of BR in other detergent solutions. That prolongation may originate from a much more severe restriction of conformational changes of BR imposed by the copolymers.…”

A block-copolymer hydrogel encapsulates bacteriorhodopsin and produces the longest photochromic response of the membrane protein under high water content conditions

“…On the other hand, active proteins themselves are not perfect material matrices considering capability of processing etc., and a composite with BRs embedded into a polymeric matrix is thus a reasonable choice. [23][24][25] This Communication reports the longest so far M decay of BR in a BR-hydrogel composite material with high water content. The photochromism between the M state and the ground state of this hydrogel material was prolonged to about a half hour.…”

“…A point mutant of D96N with the 96th residue from aspartic acid (D) to asparagine (N) was used, and an amphiphilic macromonomer with the chemical structure shown in Scheme 1 was employed. While point mutation, [26][27][28][29][30] addition of small molecules as chemical additives (crown ether 24 and arginine 31 etc.) and chemical gelling 24,25 have been applied in order to prolong the lifetime of the M intermediate in the literature, the introduction of amphiphilic macromonomers in this Communication is novel and exhibits a surprising effect.…”

“…While point mutation, [26][27][28][29][30] addition of small molecules as chemical additives (crown ether 24 and arginine 31 etc.) and chemical gelling 24,25 have been applied in order to prolong the lifetime of the M intermediate in the literature, the introduction of amphiphilic macromonomers in this Communication is novel and exhibits a surprising effect.…”