Geschwindigkeit ist alles: Damit ein Azofarbstoff für die Echtzeit‐Datenübermittlung geeignet ist, muss er nach Photoisomerisierung in seine metastabile cis‐Form eine schnelle thermische Isomerisierung zurück zur trans‐Form eingehen. Das gezeigte Azopyrimidin hat eine Relaxationszeit τ von nur 40 ns unter physiologischen Bedingungen und ist hoch biokompatibel, wie durch das Wachstum von Escherichia coli in seiner Gegenwart belegt wird (siehe Bild).

In Pseudomonas aeruginosa, Ttg2D is the soluble periplasmic phospholipid-binding component of an ABC transport system thought to be involved in maintaining the asymmetry of the outer membrane. Here we use the crystallographic structure of Ttg2D at 2.5 Å resolution to reveal that this protein can accommodate four acyl chains. Analysis of the available structures of Ttg2D orthologs shows that they conform a new substrate-binding-protein structural cluster. Native and denaturing mass spectrometry experiments confirm that Ttg2D, produced both heterologously and homologously and isolated from the periplasm, can carry two diacyl glycerophospholipids as well as one cardiolipin. Binding is notably promiscuous, allowing the transport of various molecular species. In vitro binding assays coupled to native mass spectrometry show that binding of cardiolipin is spontaneous. Gene knockout experiments in P. aeruginosa multidrug-resistant strains reveal that the Ttg2 system is involved in low-level intrinsic resistance against certain antibiotics that use a lipid-mediated pathway to permeate through membranes.

The complexation of the macrocyclic cavitand cucurbit[7]uril (Q7) with a series of amino acids (AA) with different side chains (Asp, Asn, Gln, Ser, Ala, Val, and Ile) is investigated by ESI-MS techniques. The 1:1 [Q7 + AA + 2H](2+) adducts are observed as the base peak when equimolar Q7:AA solutions are electrosprayed, whereas the 1:2 [Q7 + 2AA + 2H](2+) dications are dominant when an excess of the amino acid is used. A combination of ion mobility mass spectrometry (IM-MS) and DFT calculations of the 1:1 [Q7 + AA + 2H](2+) (AA = Tyr, Val, and Ser) adducts is also reported and proven to be unsuccessful at discriminating between exclusion or inclusion-type conformations in the gas phase. Collision induced dissociation (CID) revealed that the preferred dissociation pathways of the 1:1 [Q7 + AA + 2H](2+) dications are strongly influenced by the identity of the amino acid side chain, whereas ion molecule reactions towards N-butylmethylamine displayed a common reactivity pattern comprising AA displacement. Special emphasis is given on the differences between the gas-phase behavior of the supramolecular adducts with amino acids (AA = Asp, Asn, Gln, Ser, Ala, Val, and Ile) and those featuring basic (Lys and Arg) and aromatic (Tyr and Phe) side chains.

In cancer, proliferation of malignant cells is driven by overactivation of growth‐signalling mechanisms, such as the epidermal growth factor receptor (EGFR) pathway. Despite its therapeutic relevance, the EGF–EGFR interaction has remained elusive to inhibition by synthetic molecules, mostly as a result of its large size and lack of binding pockets and cavities. Designed peptides, featuring cyclic motifs and other structural constraints, have the potential to modulate such challenging protein–protein interactions (PPIs). Herein, we present the structure‐based design of a series of bicyclic constrained peptides that mimic an interface domain of EGFR and inhibit the EGF–EGFR interaction by targeting the smaller partner (i.e., EGF). This design process was guided by the integrated use of in silico methods and biophysical techniques, such as NMR spectroscopy and surface acoustic wave. The best analogues were able to reduce selectively the viability of EGFR+ human cancer cells. In addition to their efficacy, these bicyclic peptides are endowed with exceptional stability and metabolic resistance—two features that make them suitable candidates for in vivo applications.

We describe furan as a triggerable ‘warhead’ for site-specific cross-linking using the actin and thymosin β4 (Tβ4)-complex as model of a weak and dynamic protein-protein interaction with known 3D structure...

Despite the biological relevance of glycosyltrasferases (GTs) and the many efforts devoted to this subject, the catalytic mechanism through which a subclass of this large family of enzymes, namely those that operate with net retention of the anomeric configuration, has not been fully established. Here, we show that in the absence of an acceptor, an archetypal retaining GT such as Pyrococcus abyssi glycogen synthase (PaGS) reacts with its glucosyl donor substrate, uridine 5'‐diphosphoglucose (UDP‐Glc), to produce the scission of the covalent bond between the terminal phosphate oxygen of UDP and the sugar ring. X‐ray diffraction analysis of the PaGS/UDP‐Glc complex shows no electronic density attributable to the UDP moiety, but establishes the presence in the active site of the enzyme of a glucose‐like derivative that lacks the exocyclic oxygen attached to the anomeric carbon. Chemical derivatization followed by gas chromatography/mass spectrometry of the isolated glucose‐like species allowed us to identify the molecule found in the catalytic site of PaGS as 1,5‐anhydro‐D‐arabino‐hex‐1‐enitol (AA) or its tautomeric form, 1,5‐anhydro‐D‐fructose. These findings are consistent with a stepwise SNi‐like mechanism as the modus operandi of retaining GTs, a mechanism that involves the discrete existence of an oxocarbenium intermediate. Even in the absence of a glucosyl acceptor, glycogen synthase (GS) promotes the formation of the cationic intermediate, which, by eliminating the proton of the adjacent C2 carbon atom, yields AA. Alternatively, these observations could be interpreted assuming that AA is a true intermediate in the reaction pathway of GS and that this enzyme operates through an elimination/addition mechanism. © 2012 IUBMB Life, 64(7): 649–658, 2012.

Control of the properties of molecules, for example, their magnetic, [1] electrical, [2] or optical [3] properties, through an external trigger signal is a very interesting design feature of new promising functional systems and smart materials. Indeed, switchable materials have been explored during the last decade within materials science for a wide range of applications, such as micropumps or autonomous valves, [4] photoactive polymers that mimic cilia movement, [5] artificial musclelike actuators, [6] molecular rotary motors, [7] and photooscillators. [8] Furthermore, the precise spatial and temporal control of the information transmission of organisms through the application of suitable input energies has become an important topic in cell biology. [9] Light-responsive materials are a very attractive possibility, since optical triggering has many advantages over both chemical and electrical stimulation. Light is a clean, fast, and environmentally friendly energy source, which can be projected onto a specific position of the target system with great accuracy in a wireless, noninvasive fashion. These useful features have inspired the development of many photoswitching systems whose temporal response range is limited only by the kinetics of the chromophore that acts as a molecular switch.Azobenzene is doubtless the most widely used organic chromophore for photoswitching applications in biological systems, since it can be successfully incorporated into all types of biopolymers (including peptides, proteins, sugars, and DNA). [10] Azobenzene derivatives can be photoisomerized cleanly to their metastable cis form with the appropriate light source in just a few nanoseconds or even more rapidly. Isomerization induces a pronounced change in the optical properties of the system. The reverse process can be induced either by visible light or thermally. [11] Thermal induction of the reverse process is preferred for applications that require real-time information transmission, as it avoids the use of a second optical stimulus for active regeneration of the sample. For this goal to be met, it is essential that the azo dye exhibit a fast thermal cis-to-trans back conversion, preferably on a sub-microsecond time scale.Azo dyes that combine a strong push-pull configuration with the ability to establish an azo-hydrazone tautomeric equilibrium are promising chromophores for this purpose, since they show very fast thermal cis-to-trans isomerization kinetics at room temperature. [12] Specifically, we recently described the use of hydroxyazopiridinium salts for photoswitching applications; these compounds exhibit relaxation times as low as 33 ms at 298 K. [13] Nevertheless, it remains a challenge to increase the isomerization rate of azophenols sufficiently for their isomerization to occur on a sub-microsecond time scale.Herein we report the synthesis and thermal cis-to-trans isomerization kinetics of a new highly biocompatible pyrimidine-based azophenol (Scheme 1) that exhibits thermalrelaxation times on the nanosecond time scale ...

Epidermal growth factor receptor (EGFR) is a key target in chemotherapy. Some drugs acting on the receptor are currently in use; however, drug resistance, which causes tumour relapse, calls for the discovery of alternative inhibitors. Using docking and receptor hotspot mimicry, we have designed novel peptides directed at EGF, the main growth factor ligand of EGFR. An array of biophysical techniques was used to characterise the structure and interaction of these ligands with the target protein. Both design methods identified peptides able to bind EGF, and the capacity of these peptides to inhibit the interaction between EGF and EGFR was demonstrated in two in vitro systems. Based on targeting the smaller companion of a protein-protein interaction, the new approach described herein can be envisaged as a parallel drug design strategy, and our compounds represent the first in a new class of binders that could serve as complementary compounds in potential multidrug cancer therapy.