Switching of an Azobenzene-Tripod Molecule on Ag(111)

The trans-cis isomerization makes azobenzene (AB) a robust molecular switch. Once adsorbed to a metal, however, the switching is inefficient or absent due to rapid excited-state quenching or loss of the trans-cis bistability. We find that tris-[4-(phenylazo)-phenyl]-amine is a rather efficient switch on Ag(111). Using scanning tunneling and atomic force microscopy at submolecular resolution along with density functional theory calculations, we show that the switching process is no trans-cis isomerization but rather a reorientation of the N-N bond of an AB unit. It proceeds through a twisting motion of the azo-bridge that leads to a lateral shift of a phenyl ring. Thus, the role of the Ag substrate is ambivalent. While it suppresses the original bistability of the azobenzene units, it creates a new one by inducing a barrier for the rotation of the N-N bond

Broken Symmetry of an Adsorbed Molecular Switch Determined by Scanning Tunneling Spectroscopy

Scanning tunneling spectroscopy has been used to analyze the structure of tris[4-(phenylazo)phenyl)]amine on a Au(111) surface. A degenerate marker state serves as a sensitive probe for the structure of the adsorbed molecules

Broken Symmetry of an Adsorbed Molecular Switch Determined by Scanning Tunneling Spectroscopy

Die Struktur von Tris[4-(phenylazo)phenyl)]amin auf einer Au(111)-Oberfläche wurde mit Rastertunnelspektroskopie untersucht. Ein entarteter Markerzustand dient als empfindliche Sonde für die Struktur der adsorbierten Moleküle

Effect of arginine on the aggregation of protein in freeze-dried Formulations containing sugars and polyol: 1-formulation development

L-arginine was introduced into protein-based freeze-dried formulations to study the ability of arginine to reduce/prevent from protein aggregation during manufacturing, storage and reconstitution of lyophilized protein-based pharmaceuticals. As L-arginine is known to be very hygroscopic, additional excipients which could provide a moisture buffering capacity need to be introduced into the formulation. In the first part of our study-excipient formulation development-the screening of a number of sugars/polyols has been done in order to select the best combination of excipients that, in a complex with L-arginine, can (i) produce freeze-dried cakes with elegant appearance, adequate mechanical properties and reconstitution times, and (ii) resist/minimise the moisture sorption. Various freeze-dried cakes containing L-arginine in combination with mannitol, trehalose, lactose and sucrose were produced and analysed by TGA, DSC, texture analysis, moisture sorption, cake shrinkage, TVIM and SEM. The non-linear dependencies of the physicochemical properties of the freeze-dried cakes on the sugar-to-mannitol ratios were found. The best combinations of excipients (L-arginine, mannitol and trehalose) were selected to be used in the second part of this work, in which the impact of each selected formulation will be studied in relation to the aggregation of a protein

Insights on the formulation of recombinant proteins

Recombinant proteins are large and complex molecules, whose therapeutic activity highly depends on their structure. Formulation of biopharmaceuticals aims at stabilizing protein conformation, promoting its efficacy, and preventing safety concerns, such as immunogenicity. Currently, the rational design of formulations is possible due to the availability of several techniques for molecule characterization and an array of both well-known and new excipients. Also, high-throughput technologies and Quality by Design approaches are trending and have been contributing to the advancement of the field. Still, there is a search for alternatives that ensure quality of the medicines through its life cycle, particularly for highly concentrated formulations, such as monoclonal antibodies. There is also a demand for strategies that improve protein delivery and more comfortable administration to the patients, especially with the arising of recombinant proteins in the treatment of chronic diseases, such as autoimmune conditions or heart diseases. In this chapter, current and future advancements regarding recombinant protein formulation and its impact in drug development and approval will be addressed.info:eu-repo/semantics/publishedVersio