The modification of proteins with non-protein entities is important for a wealth of applications, and methods for chemically modifying proteins attract considerable attention. Generally, modification is desired at a single site to maintain homogeneity and to minimise loss of function. Though protein modification can be achieved by targeting some natural amino acid side chains, this often leads to ill-defined and randomly modified proteins. Amongst the natural amino acids, cysteine combines advantageous properties contributing to its suitability for site-selective modification, including a unique nucleophilicity, and a low natural abundance--both allowing chemo- and regioselectivity. Native cysteine residues can be targeted, or Cys can be introduced at a desired site in a protein by means of reliable genetic engineering techniques. This review on chemical protein modification through cysteine should appeal to those interested in modifying proteins for a range of applications.

Growth and development are coordinated by an array of intercellular communications. Known plant signaling molecules include phytohormones and hormone peptides. Although both classes can be implicated in the same developmental processes, little is known about the interplay between phytohormone action and peptide signaling within the cellular microenvironment. We show that genes coding for small secretory peptides, designated GOLVEN (GLV), modulate the distribution of the phytohormone auxin. The deregulation of the GLV function impairs the formation of auxin gradients and alters the reorientation of shoots and roots after a gravity stimulus. Specifically, the GLV signal modulates the trafficking dynamics of the auxin efflux carrier PIN-FORMED2 involved in root tropic responses and meristem organization. Our work links the local action of secretory peptides with phytohormone transport.

Receptor-mediated endocytosis is an integral part of signal transduction as it mediates signal attenuation and provides spatial and temporal dimensions to signaling events. One of the best-studied leucine-rich repeat receptor-like kinases in plants, BRASSINOSTEROID INSENSITIVE 1 (BRI1), perceives its ligand, the brassinosteroid (BR) hormone, at the cell surface and is constitutively endocytosed. However, the importance of endocytosis for BR signaling remains unclear. Here we developed a bioactive, fluorescent BR analog, Alexa Fluor 647-castasterone (AFCS), and visualized the endocytosis of BRI1-AFCS complexes in living Arabidopsis thaliana cells. Impairment of endocytosis dependent on clathrin and the guanine nucleotide exchange factor for ARF GTPases (ARF-GEF) GNOM enhanced BR signaling by retaining active BRI1-ligand complexes at the plasma membrane. Increasing the trans-Golgi network/early endosome pool of BRI1-BR complexes did not affect BR signaling. Our findings provide what is to our knowledge the first visualization of receptor-ligand complexes in plants and reveal clathrin- and ARF-GEF-dependent endocytic regulation of BR signaling from the plasma membrane.

Long, multifunctional sequence-defined oligomers were obtained on solid support from a protecting-group-free two-step iterative protocol, based on the inherent reactivity of a readily available molecule containing an isocyanate and a thiolactone. Aminolysis of the latter entity with an amino alcohol liberates a thiol that reacts with an acrylate or acrylamide, present in the same medium. Subsequently, a new thiolactone can be reinstated by means of an α-isocyanato-γ-thiolactone. Different acrylic compounds were used to incorporate diverse functionalities in the oligomers, which were built up to the level of decamers. The reaction conditions were closely monitored in order to fine-tune the applied strategy as well as facilitate the translation to an automated protocol.

The aim of this review is to make researchers aware of the benefits of an efficient quality control system for prediction of a developed vaccine's efficacy. Two major goals should be addressed when inactivating a virus for vaccine purposes: first, the infectious virus should be inactivated completely in order to be safe, and second, the viral epitopes important for the induction of protective immunity should be conserved after inactivation in order to have an antigen of high quality. Therefore, some problems associated with the virus inactivation process, such as virus aggregate formation, protein crosslinking, protein denaturation and degradation should be addressed before testing an inactivated vaccine in vivo