Fmoc-3,4-dehydro-L-Val-OH

Ordered supramolecular hydrogels assembled by modified aromatic amino acids often exhibit low mechanical rigidity. Aiming to stabilize the hydrogel and understand the impact of conformational freedom and hydrophobicity on the self-assembly process, two building blocks based on 9-fluorenyl-methoxycarbonyl-phenylalanine (Fmoc-Phe) gelator which contain two extra methylene units in the backbone, generating Fmoc-γPhe and Fmoc-(3-hydroxy)-γPhe are designed. Fmoc-γPhe spontaneously assembled in aqueous media forming a hydrogel with exceptional mechanical and thermal stability. Moreover, Fmoc-(3-hydroxy)-γPhe, with an extra backbone hydroxyl group decreasing its hydrophobicity while maintaining some molecular flexibility, self-assembled into a transient fibrillar hydrogel, that later formed microcrystalline aggregates through a phase transition. Molecular dynamics simulations and single crystal X-ray analyses reveal the mechanism underlying the two residues' distinct self-assembly behaviors. Finally, Fmoc-γPhe and Fmoc-(3-OH)-γPhe co-assembly to form a supramolecular hydrogel with notable mechanical properties are demonstrated. It has been believed that the understanding of the structure-assembly relationship will enable the design of new functional amino acid-based hydrogels.

3-Methyl-1-butanol (3MB) is a promising biofuel that can be produced from 2-ketoisocaproate via the common L-leucine biosynthesis pathway. Corynebacterium glutamicum was chosen as a host bacterium because of its strong resistance to isobutanol. In the current study, several strategies were designed to overproduce 3MB in C. glutamicum through a non-fermentation pathway. The engineered C. glutamicum mutant was obtained by silencing the pyruvate dehydrogenase gene complex (aceE) and deleting the lactic dehydrogenase gene (ldh), followed by mutagenesis with diethyl sulfate (DES) and selection with Fmoc-3-4-thiazolyl-L-alanine (FTA). The mutant could produce 659 mg/L of 3MB after 12 h of incubation. To facilitate carbon flux to 3MB biosynthesis, the engineered recombinant was also constructed without branched-chain acid aminotransferase (ilvE) activity by deleting the ilvE gene. This recombinant could produce 697 mg/L of 3MB after 12 h of incubation.

Fmoc-3-nitrotyrosine (Fmoc-3-NT) molecularly imprinted polymers (MIPs) were synthesized to understand the influence of several functional monomers on the efficiency of the molecular imprinting process. Acidic, neutral and basic functional monomers, such as acrylic acid (AA), methacrylic acid (MAA), methacrylamide (MAM), 2-vinylpyridine (2-VP), 4-vinylpyridine (4-VP), have been used to synthesize five different polymers. In this study, the MIPs were tested in batch experiments by UV-visible spectroscopy in order to evaluate their binding properties. The MIP prepared with 2-VP exhibited the highest binding affinity for Fmoc-3NT, for which Scatchard analysis the highest association constant (2.49 × 10(4) M(-1)) was obtained. Furthermore, titration experiments of Fmoc-3NT into acetonitrile solutions of 2-VP revealed a stronger bond to the template, such that a total interaction is observed. Non-imprinted polymers as control were prepared and showed no binding affinities for Fmoc-3NT. The results are indicative of the importance of ionic bonds formed between the -OH residues of the template molecule and the pyridinyl groups of the polymer matrix. In conclusion, 2-VP assists to create a cavity which allows better access to the analytes.