3 research outputs found
Conductivity studies of single protein molecules
A fundamental step for future uses of biomolecules in electronics is the study of
the bonding, orientation and conductance of a single molecule attached to a conductive
substrate, which is the building block of electronic materials and devices
based on molecular conduction. This work provides an in-depth examination of
morphology and electrical properties of different molecules anchored to Au(111)
and to sustainable carbon materials (graphite and graphene). Cytochrome b562
(Cyt b562), TEM beta-lactamase and the superfolded green
uorescent protein
engineered with phenyl azide were exposed to UV irradiation to transform the
azide compound into the nitrene radical, which enabled successful molecule linking
to graphene. The UV-based approach was tested on the above molecules to
ascertain its robustness against the speci�city of the protein used. The e�ciency
of the procedure was inspected by imaging via atomic force microscopy (AFM)
and scanning tunnelling microscopy (STM). By repeated sample preparation and
imaging, we established suitable protein concentrations to enable single-molecule
measurements on the resulting samples (e.g., the concentration range optimal for
cyt b562 on gold was 0.025-0.5 �M). We used a home-built environmental cell in
combination with STM to study the conductance of di�erently engineered cyt
b562 proteins on Au(111), as well as the conductance of oligothiophene on gold,
under di�erent humidity and temperature conditions. We found that the conductance
of cyt b562 is smaller at lower relative humidity and further decreased
when also temperature is reduced. Measuring the conductance as a function of
the tip-substrate distance in both tip approaching and retracting modes revealed
the occurrence of hysteresis. The engineered cyt b562 with two thiols in the long
axis led to less hysteresis in the conductance and larger protein height on gold
(from AFM) compared to the protein with thiols in the short axis. Our results
stress the importance of protein engineering to control the electrical properties of
functionalized surfaces. This study meets the growing demand for achieving more
e�cient molecule linking to conductive substrates, and studying environmental
e�ects on the electrical response of functionalized surfaces (which is relevant, e.g.,
to sensing applications)
Conductivity studies of single protein molecules
A fundamental step for future uses of biomolecules in electronics is the study of
the bonding, orientation and conductance of a single molecule attached to a conductive
substrate, which is the building block of electronic materials and devices
based on molecular conduction. This work provides an in-depth examination of
morphology and electrical properties of different molecules anchored to Au(111)
and to sustainable carbon materials (graphite and graphene). Cytochrome b562
(Cyt b562), TEM beta-lactamase and the superfolded green
uorescent protein
engineered with phenyl azide were exposed to UV irradiation to transform the
azide compound into the nitrene radical, which enabled successful molecule linking
to graphene. The UV-based approach was tested on the above molecules to
ascertain its robustness against the speci�city of the protein used. The e�ciency
of the procedure was inspected by imaging via atomic force microscopy (AFM)
and scanning tunnelling microscopy (STM). By repeated sample preparation and
imaging, we established suitable protein concentrations to enable single-molecule
measurements on the resulting samples (e.g., the concentration range optimal for
cyt b562 on gold was 0.025-0.5 �M). We used a home-built environmental cell in
combination with STM to study the conductance of di�erently engineered cyt
b562 proteins on Au(111), as well as the conductance of oligothiophene on gold,
under di�erent humidity and temperature conditions. We found that the conductance
of cyt b562 is smaller at lower relative humidity and further decreased
when also temperature is reduced. Measuring the conductance as a function of
the tip-substrate distance in both tip approaching and retracting modes revealed
the occurrence of hysteresis. The engineered cyt b562 with two thiols in the long
axis led to less hysteresis in the conductance and larger protein height on gold
(from AFM) compared to the protein with thiols in the short axis. Our results
stress the importance of protein engineering to control the electrical properties of
functionalized surfaces. This study meets the growing demand for achieving more
e�cient molecule linking to conductive substrates, and studying environmental
e�ects on the electrical response of functionalized surfaces (which is relevant, e.g.,
to sensing applications)
Functional modulation and directed assembly of an enzyme through designed non-natural post-translation modification
Post-translational modification (PTM) modulates and supplements protein functionality. In nature this high precision event requires specific motifs and/or associated modification machinery. To overcome the inherent complexity that hinders PTM's wider use, we have utilized a non-native biocompatible Click chemistry approach to site-specifically modify TEM β-lactamase that adds new functionality. In silico modelling was used to design TEM β-lactamase variants with the non-natural amino acid p-azido-L-phenylalanine (azF) placed at functionally strategic positions permitting residue-specific modification with alkyne adducts by exploiting strain-promoted azide–alkyne cycloaddition. Three designs were implemented so that the modification would: (i) inhibit TEM activity (Y105azF); (ii) restore activity compromised by the initial mutation (P174azF); (iii) facilitate assembly on pristine graphene (W165azF). A dibenzylcyclooctyne (DBCO) with amine functionality was enough to modulate enzymatic activity. Modification of TEMW165azF with a DBCO–pyrene adduct had little effect on activity despite the modification site being close to a key catalytic residue but allowed directed assembly of the enzyme on graphene, potentially facilitating the construction of protein-gated carbon transistor system