Characterization of Thermal Isomerization at the Single Molecule Level

Abstract

Single-channel measurements were used to study the cis-trans isomerization of a carbamate bond in gramicidin-ethylenediamine, a derivative of the channel-forming peptide gramicidin. From the temperature dependence of transition rates, values of 64.9 f 2.5 and 58.2 f 3.0 kJ mol-' were calculated for isomerization from the trans and cis states, respectively. The entropies of activation were calculated to be

Uni‐molecular detection and quantification of selected β‐lactam antibiotics with a hybrid α‐hemolysin protein pore

“…Perhaps the most useful information offered by investigations into the behavior and dynamics of single molecules refers to possibility of gaining insights into events that are buried under statistical averaging, and cannot be obtained from ensemble measurements (Bayley et al, 2008;Griffiths, 2008;Kasianowicz et al, 2008). To date, optical (Lu et al, 1998;Lee and Ho, 1999), force (Kersey et al, 2006), and electrical (Jaikaran and Woolley, 1995;Shin et al, 2002;Luchian et al, 2003a,b) measurements have been employed to investigate the dynamics of individual molecules in solution, and progress has been made in applying these approaches to chemical reactions.…”

Applications of biological pores in nanomedicine, sensing, and nanoelectronics

“…Woolley and co-workers used a derivative of gramicidin that carried a carbamate group near its pore entrance to monitor the temperature dependence of the rate of transition between cis and trans isomers of carbamate. Transitions from the trans to the cis isomer resulted in positioning of a protonated, and hence positively charged, amino group on the C-terminal extension closer to the entrance of the gramicidin pore; this change resulted in a detectable decrease in the channel conductance [316]. More recently, the groups of Yang and Mayer have applied gramicidin peptides for detection of more complex chemical reactions than protonation [21,33 • ,317].…”

Kinetics of a Three‐Step Reaction Observed at the Single‐Molecule Level

“…Electrical detection at the singlemolecule level has been used previously to follow a unidirectional single-step reaction, [14] to observe a thermal isomerization, [15,16] and to monitor reversible single-step covalent chemistry. [17] Finkelstein and co-workers observed the reaction of a cysteine residue in the lumen of the diphtheria toxin pore with CH 3 SO 2 SCH 2 CH 2 N(CH 3 ) 3 + .…”

“…[14] Woolley and coworkers synthesized a gramicidin with a carbamate attached near the mouth of the pore. [15,16] They were able to observe the temperature dependence of the rates of cis-trans isomerization of the carbamate and thereby determine the activation enthalpies and entropies. In our research group, the reversible reactions of organoarsenic(iii) compounds with the thiol group of a single cysteine residue projecting into the lumen of the a-hemolysin (aHL) pore have been examined.…”