Tailor-made Amino Acids Research Articles

Mono‐ and Bis(pyrrolo)tetrathiafulvalene Derivatives Tethered to C60: Synthesis, Photophysical Studies, and Self‐Assembled Monolayers

A series of mono- (MPTTF) and bis(pyrrolo)tetrathiafulvalene (BPTTF) derivatives tethered to one or two C60 moieties was synthesized and characterized. The synthetic strategy for these dumbbell-shaped compounds was based on a 1,3-dipolar cycloaddition reaction between aldehyde-functionalized MPTTF/BPTTF derivatives, two different tailor-made amino acids, and C60. Electronic communication between the MPTTF/BPTTF units and the C60 moieties was studied by a variety of techniques including cyclic voltammetry and absorption spectroscopy. These solution-based studies indicated no observable electronic communication between the MPTTF/BPTTF units and the C60 moieties. In addition, femtosecond and nanosecond transient absorption spectroscopy revealed, rather surprisingly, that no charge transfer from the MPTTF/BPTTF units to the C60 moieties takes place on excitation of the fullerene moiety. Finally, it was shown that the MPTTF-C60 and C60-BPTTF-C60 dyad and triad molecules formed self-assembled monolayers on a Au(111) surface by anchoring to C60.

The non-protein amino acid β-N-methylamino-l-alanine in Portuguese cyanobacterial isolates

The tailor made amino acid β-N-methyl-amino-L-alanine (BMAA) is a neurotoxin produced by cyanobacteria. It has been associated with certain forms of progressive neurodegenerative disease, including sporadic Amyotrophic Lateral Sclerosis and Alzheimer's disease. Some different reports of BMAA in cyanobacterial blooms from lakes, reservoirs, and other water resources have been made by different investigators. We here report the detection of BMAA of both free and protein-bound produced by cyanobacteria, belonging to the Chroococcales, Oscillatoriales and Nostocales ordered. We use a rapid and sensitive HPLC-FD method that utilizes methanol elution and the Waters AQC Tag chemistry. On other hand, we have used three different assay procedures for BMAA extraction from cyanobacteria: Trichloroacetic acid (TCA), Methanol/Acetone and hydrochloric acid (HCl). All assays let successfully detect BMAA in all cyanobacteria samples analyzed. Nevertheless, with TCA and HCl extraction procedures the highest BMAA values, for free as well as protein-bound BMAA were detected. BMAA content could not be related to the taxonomy of the isolates or to their geographical origin, and no correlation between free and protein-bound BMAA concentrations were observed within or between taxonomic groups. These data offer confirmation of the taxonomic and geographic ubiquity of BMAA from naturally occurring populations of cyanobacteria, for the first time reported for estuaries.

Anion Chelation by Amido Acid Functionalized Fused Quartz/Water Interfaces Studied by Nonlinear Optics

We report resonantly enhanced surface second harmonic generation (SHG) measurements to track the interaction of the EPA priority toxic metal pollutant chromium(VI) with fused quartz/water interfaces containing tailor-made amino acids that serve as model systems for environmental and biological interfaces. chi3 measurements of amido acid functionalized fused quartz/water interfaces are consistent with two acid-base equilibria, suggesting the formation of a laterally hydrogen-bonded environment similar to what is observed for aliphatic carboxylic acids. Chromate adsorption isotherms recorded at pH 7 are suggestive of an intramolecular chelation mechanism that becomes important when four or more hydrogen-bonding moieties are displayed toward the incoming chromate. The strong binding affinities of the amido acid functionalized fused quartz/water interfaces toward chromate are consistent with nearly 50% slower transport rates with respect to free-flowing groundwater, indicating that, in the absence of redox processes, peptide materials in heterogeneous geochemical environments can significantly increase chromate residence times. The strong evidence for synergistic effects dominating the interactions of chromate with surface-bound amido acids indicates that chemical complexity can be systematically addressed using tailor-made organic surfaces and interfaces.

Incorporation of spin-labelled amino acids into proteins

The elucidation of structure and function of proteins and membrane proteins by EPR spectroscopy has become increasingly important in recent years as technological advances have been made in the design of spectrometers and in the chemistry of the nitroxide group. These new developments have increased the demand for tailor-made amino acids carrying a spin label on the one hand and for reliable methods for their incorporation into proteins on the other. Here we describe methods for site-specific spin labelling of proteins. It is shown that a combination of recombinant synthesis of proteins with chemically produced peptides (expressed protein ligation) allows the preparation of site-specifically spin-labelled proteins.