Aspartame and aspartame derivatives effect human thrombin catalytic activity

Structural elucidation of dipeptides displaying limited mass spectral information by liquid chromatography-electrospray ionization-tandem mass spectrometry

Small peptides, such as dipeptides, have attracted attention in many research fields because of their important biological functions and potential roles as disease biomarkers. However, the identification of many of them by implementation of liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) is a challenging task. This is because many dipeptides display limited mass spectral information in LC-ESI-MS/MS analyses, which leads to unavoidable ambiguity in determinations of their structures. In this study, two useful analytical techniques were developed for the structural elucidation of 10 representative dipeptides exhibiting a dominant/single product ion in the ESI-MS/MS spectra of the protonated molecules [M + H]⁺ . Structural elucidation was obtained instantaneously through LC-ESI-MS/MS fragmentation of the accompanying sodium adducts [M + Na]⁺ or alternatively by "in-vial" chemical derivatization with isobutyl chloroformate. The sodium adducts and the resulting carbamate derivatives altered the charge distribution occurring during ESI-MS/MS fragmentation, enabling detailed structural elucidation and unambiguous identification of such dipeptides at ng/ml levels. These quick, simple, and easy techniques can be implemented to identify various dipeptides or confirm their identities without the need for complex sample handling.

One-pot synthesis of alternating peptides exploiting a new polymerization technique based on Ugi's 4CC reaction

A catalyst-free, one-pot synthetic technique for alternating peptides was developed on the basis of Ugi's 4 component condensation reaction.

Ultrastructural changes to rabbit fibrin and platelets due to aspartame

The coagulation process, including thrombin, fibrin, as well as platelets, plays an important role in hemostasis, contributing to the general well-being of humans. Fibrin formation and platelet activation are delicate processes that are under the control of many small physiological events. Any one of these many processes may be influenced or changed by external factors, including pharmaceutical or nutritional products, e.g., the sweetener aspartame (L-aspartyl-L-phenylalanine methyl ester). It is known that phenylalanine is present at position P(9) and aspartate at position P(10) of the alpha-chain of human fibrinogen, and plays an important role in the conversion of fibrinogen to fibrin by the catalyst alpha-thrombin. The authors investigate the effect of aspartame on platelet and fibrin ultrastructure, by using the rabbit animal model and the scanning electron microscope. Animals were exposed to 34 mg/kg of aspartame 26x during a 2-month period. Aspartame-exposed fibrin networks appeared denser, with a thick matted fine fiber network covering thick major fibers. Also, the platelet aggregates appeared more granular than the globular control platelet aggregates. The authors conclude by suggesting that aspartame usage may interfere with the coagulation process and might cause delayed fibrin breakup after clot formation. They suggest this, as the fibrin networks from aspartame-exposed rabbits are more complex and dense, due to the netlike appearance of the minor, thin fibers. Aspartame usage should possibly be limited by people on anti-clotting medicine or those with prone to clot formation.