Adsorption of proteins onto solid surfaces is an everyday phenomenon that is not yet fully understood. To further the current understanding, we have performed in situ ellipsometry studies to reveal the adsorption kinetics of three different proteins, lysozyme, α-amylase and bovine serum albumin. As substrates we offer Si wafers with a controlled Si oxide layer thickness and a hydrophilic or hydrophobic surface functionalization, allowing the tailoring of the influence of short- and long-range interactions. Our studies show that not only the surface chemistry determines the properties of an adsorbed protein layer but also the van der Waals contributions of a composite substrate. We compare the experimental findings to results of a colloidal Monte Carlo approach that includes conformational changes of the adsorbed proteins induced by density fluctuations.
The treatment of 2,2'-di(1,2-pyrazol-3-yl)-1,1'-binaphthyl with two equivalents of appropriate monovalent group 11 precursors in the presence of a base leads to a complete exchange of the pyrazole NH protons with M(+) cations. Structural characterisation of the copper(I) complex revealed a hexanuclear complex with a pelton-wheel-like arrangement of the binaphthyl unit. As indicated by their spectroscopic data, all three complexes are isostructural. The complexes show a complex fluorescence behaviour that can be partially related to the ligand system and also to the metal sites, as indicated by the position of the fluorescence peaks and their temperature dependence and lifetimes.
The control of biofilm formation is a challenging goal that has not been reached yet in many aspects. One unsolved question is the role of van der Waals forces and another is the importance of mutual interactions between the adsorbing and the adsorbed biomolecules ͑"critical crowding"͒. In this study, a combined experimental and theoretical approach is presented, which fundamentally probes both aspects. On three model proteins-lysozyme, ␣-amylase, and bovine serum albumin-the adsorption kinetics is studied experimentally. Composite substrates are used enabling a separation of the short-and the long-range forces. Although usually neglected, experimental evidence is given for the influence of van der Waals forces on the protein adsorption as revealed by in situ ellipsometry. The three proteins were chosen for their different conformational stabilities in order to investigate the influence of conformational changes on the adsorption kinetics. Monte Carlo simulations are used to develop a model for these experimental results by assuming an internal degree of freedom to represent conformational changes. The simulations also provide data on the distribution of adsorption sites. By in situ atomic force microscopy we can also test this distribution experimentally, which opens the possibility to, e.g., investigate the interactions between adsorbed proteins.
Di‐, tri‐, and tetrathienyl‐substituted polycyclic aromatic fluorophores were prepared from different aryldi‐, aryltri‐, or aryltetrahalides by a simple and fast Suzuki coupling. The reaction was optimized for the synthesis of the desired materials on multigram scale. The coupled products were converted into the corresponding iodides through iodination with N‐iodosuccinimide. The iodides turned out to be versatile starting materials for applications, such as periodic mesoporous organosilica syntheses. They were converted into a variety of new trimethoxysilyl arenes by using a very efficient Pd‐mediated C–Si cross‐coupling, which was also extended to the corresponding thienyl bromides by using a dimeric PdI catalyst. All compounds were characterized by 1H NMR, 13C NMR, 29Si NMR, and ATR‐IR spectroscopy and HRMS.
The spectral properties of fluorescence sensors such as 3-hydroxychromone (3-HC) and its derivatives are sensitive to interaction with the surrounding medium as well as to substitution. 3-HC is a prototype system for other derivatives because it is the basic unit of all flavonoides undergoing ESIPT and is not perturbed by a substituent. In this study, the elementary processes and intermediate states in the photocycle of 3-HC as well as its anion were identified and characterized by the use of static and femtosecond time-resolved spectroscopy in different solvents (methylcyclohexane, acetonitrile, ethanol, and water at different pH). Electronic absorption and fluorescence spectra and lifetimes of the intermediate states were obtained for the normal, tautomer and anionic excited state, while mid-IR vibrational spectra yielded structural information on ground and excited states of 3-HC. A high sensitivity on hydrogen-bonding perturbations was observed, leading to photoinduced anion formation in water, while in organic solvents, different processes are suggested, including slow picosecond ESIPT and contribution of the trans-structure excited state or a different stable solvation state with different direction of OH. The formation of the latter could be favored by the lack of a substituent increasing contact points for specific solute-solvent interactions at the hydroxyl group compared to substituted derivatives. The effect of substituents has to be considered for the design of future fluorescence sensors based on 3-HC.
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