Apertureless scanning near-field optical microscopy of sparsely labeled tobacco mosaic viruses and the intermediate filament desmin

Plant virus-based materials for biomedical applications: Trends and prospects

Nanomaterials composed of plant viral components are finding their way into medical technology and health care, as they offer singular properties. Precisely shaped, tailored virus nanoparticles (VNPs) with multivalent protein surfaces are efficiently loaded with functional compounds such as contrast agents and drugs, and serve as carrier templates and targeting vehicles displaying e.g. peptides and synthetic molecules. Multiple modifications enable uses including vaccination, biosensing, tissue engineering, intravital delivery and theranostics. Novel concepts exploit self-organization capacities of viral building blocks into hierarchical 2D and 3D structures, and their conversion into biocompatible, biodegradable units. High yields of VNPs and proteins can be harvested from plants after a few days so that various products have reached or are close to commercialization. The article delineates potentials and limitations of biomedical plant VNP uses, integrating perspectives of chemistry, biomaterials sciences, molecular plant virology and process engineering.

Molecular insights into cardiomyopathies associated with desmin (DES) mutations

Increasing usage of next-generation sequencing techniques pushed during the last decade cardiogenetic diagnostics leading to the identification of a huge number of genetic variants in about 170 genes associated with cardiomyopathies, channelopathies, or syndromes with cardiac involvement. Because of the biochemical and cellular complexity, it is challenging to understand the clinical meaning or even the relevant pathomechanisms of the majority of genetic sequence variants. However, detailed knowledge about the associated molecular pathomechanism is essential for the development of efficient therapeutic strategies in future and genetic counseling. Mutations in DES, encoding the muscle-specific intermediate filament protein desmin, have been identified in different kinds of cardiac and skeletal myopathies. Here, we review the functions of desmin in health and disease with a focus on cardiomyopathies. In addition, we will summarize the genetic and clinical literature about DES mutations and will explain relevant cell and animal models. Moreover, we discuss upcoming perspectives and consequences of novel experimental approaches like genome editing technology, which might open a novel research field contributing to the development of efficient and mutation-specific treatment options.

Dual Functionalization of Rod-Shaped Viruses on Single Coat Protein Subunits

Plant viruses are emerging as versatile tools for nanotechnology applications since it is possible to modify their multivalent protein surfaces and thereby introduce and display new functionalities. In this chapter, we describe a tobacco mosaic virus (TMV) variant that exposes two selectively addressable amino acid moieties on each of its 2130 coat protein (CP) subunits. A lysine as well as a cysteine introduced at accessible sites of every CP can be modified with amino- and/or thiol-reactive chemistry such as N-hydroxysuccinimide esters (NHS ester) and maleimide containing reagents alone or simultaneously. This enables the pairwise immobilization of distinct molecules in close vicinity to each other on the TMV surface by simple standard conjugation protocols. We describe the generation of the mutations, the virus propagation and isolation as well as the dual functionalization of the TMV variant with two fluorescent dyes. The labeling is evaluated by SDS-PAGE and spectrophotometry and the degree of labeling (DOL) calculated.

Dynamic DNA-controlled "stop-and-go" assembly of well-defined protein domains on RNA-scaffolded TMV-like nanotubes

A DNA-based approach allows external control over the self-assembly process of tobacco mosaic virus (TMV)-like ribonucleoprotein nanotubes: their growth from viral coat protein (CP) subunits on five distinct RNA scaffolds containing the TMV origin of assembly (OAs) could be temporarily blocked by a stopper DNA oligomer hybridized downstream (3') of the OAs. At two upstream (5') sites tested, simple hybridization was not sufficient for stable stalling, which correlates with previous findings on a non-symmetric assembly of TMV. The growth of DNA-arrested particles could be restarted efficiently by displacement of the stopper via its toehold by using a release DNA oligomer, even after storage for twelve days. This novel strategy for growing proteinaceous tubes under tight kinetic and spatial control combines RNA guidance and its site-specific but reversible interruption by DNA blocking elements. As three of the RNA scaffolds contained long heterologous non-TMV sequence portions that included the stopping sites, this method is applicable to all RNAs amenable to TMV CP encapsidation, albeit with variable efficiency most likely depending on the scaffolds' secondary structures. The use of two distinct, selectively addressable CP variants during the serial assembly stages finally enabled an externally configured fabrication of nanotubes with highly defined subdomains. The "stop-and-go" strategy thus might pave the way towards production routines of TMV-like particles with variable aspect ratios from a single RNA scaffold, and of nanotubes with two or even more adjacent protein domains of tightly pre-defined lengths.

High-Resolution Kelvin Probe Force Microscopy Imaging of Interface Dipoles and Photogenerated Charges in Organic Donor-Acceptor Photovoltaic Blends

We present noncontact atomic force microscopy and Kelvin probe force microscopy studies of nanophase segregated photovoltaic blends based on an oligothiophene-fluorenone oligomer and [6,6]-phenyl C70 butyric acid methyl ester. We carried out a complete analysis of the influence of the tip-surface interaction regime on the topographic, in-dark contact potential and surface photovoltage contrasts. It is demonstrated that an optimal lateral resolution is achieved for all channels below the onset of a contrast in the damping images. With the support of electrostatic simulations, it is shown that in-dark contact potential difference contrasts above subsurface acceptor clusters are consistent with an uneven distribution of permanent charges at the donor-acceptor interfaces. A remarkable dependence of the surface photovoltage magnitude with respect to the tip-surface distance is evidenced and attributed to a local enhancement of the electromagnetic field at the tip apex.

Single virus detection by means of atomic force microscopy in combination with advanced image analysis

In the present contribution virions of five different virus species, namely Varicella-zoster virus, Porcine teschovirus, Tobacco mosaic virus, Coliphage M13 and Enterobacteria phage PsP3, are investigated using atomic force microscopy (AFM). From the resulting height images quantitative features like maximal height, area and volume of the viruses could be extracted and compared to reference values. Subsequently, these features were accompanied by image moments, which quantify the morphology of the virions. Both types of features could be utilized for an automatic discrimination of the five virus species. The accuracy of this classification model was 96.8%. Thus, a virus detection on a single-particle level using AFM images is possible. Due to the application of advanced image analysis the morphology could be quantified and used for further analysis. Here, an automatic recognition by means of a classification model could be achieved in a reliable and objective manner.