Ff filamentous phage (fd, M13 and f1) of Escherichia coli have been the workhorse of phage display technology for the past 30 years. Dominance of Ff over other bacteriophage in display technology stems from the titres that are about 100-fold higher than any other known phage, efficacious transformation ensuring large library size and superior stability of the virion at high temperatures, detergents and pH extremes, allowing broad range of biopanning conditions in screening phage display libraries. Due to the excellent understanding of infection and assembly requirements, Ff phage have also been at the core of phage-assisted continual protein evolution strategies (PACE). This chapter will give an overview of the Ff filamentous phage structure and biology, emphasizing those properties of the Ff phage life cycle and virion that are pertinent to phage display applications.
The bromine‐chlorine dianionic octahalide‐containing salts [C3(NEt2)3]2[Br4Cl4] (1c) and [C3(NEt2)3]2[Br3Cl5] (2d) were prepared using the triaminocyclopropenium cation as a template. The salt 1c was prepared in two steps, firstly, either by addition of BrCl to the triaminocyclopropenium chloride salt [C3(NEt2)3]Cl or addition of Cl2 to the bromide salt [C3(NEt2)3]Br to form the trihalide [BrCl2]– salt, secondly, addition of half an equivalent of Br2 gave the desired product upon crystallization at low temperature. Salt 2d is prepared by addition of excess BrCl to [C3(NEt2)3]Cl. Both salts are best described as two trihalides bridged by a dihalogen. When the tetraethylammonium cation is used, a salt of the formula [NEt4]2[Br4.56Cl0.44][ClBr2] (4), containing disordered [ClBr2]– and a chain of [ClBr4]– and [Br5]– pentahalides (in a ratio of 0.44 to 0.56, respectively). These interhalides were characterized by X‐ray crystallography, computational studies, Raman and Far‐IR spectroscopy, as well as by TGA and melting point.
We report a set of resonantly enhanced defect modes in
the Raman
spectrum of molybdenum disulfide (MoS2) which are fully
analogous to the D mode of graphene, allowing sensitive defect quantification
and differentiation of zigzag and armchair edge structures. These
modes become active at edges under indirect resonance conditions at
785 nm excitation due to strict backscatter constraints in real and
reciprocal space, which exclusively select phonon wavevectors perpendicular
to the edge direction. We assign features to single LA(K), TA(K),
and TA(Q) phonons along the
direction of the Brillouin zone and identify
a separate preresonant enhancement of the whole spectrum along the
direction, which is lost in thinner material
as the band gap increases. In addition, we identify a clear incident
polarization dependence of the K and M phonons, which suggests the
presence of an inhomogeneous optical absorption analogous to that
of graphene. We anticipate this indirect double resonance Raman technique
will provide a powerful tool for materials characterization, allowing
quantification of active sites in catalytic MoS2 and characterization
of the structure-dependent properties of MoS2 nanomaterials.
In addition, the intervalley scattering pathways provide a sensitive
probe of the low energy landscape of the conduction band and may reveal
a wealth of electronic information and scattering dynamics important
for spin–valley coupled systems. We anticipate similar modes
can be found in other transition metal dichalcogenide systems, given
the appropriate excitation energy.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.