Chemical biology of molecular interaction between tea catechins with biological substances

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1.The association constants obtained from the frequency changes of quartz-crystal microbalance(QCM) revealed interactions of ECg and EGCg with HSA that are 100 times stronger than those of EC and EGC.2.The most important structural element contributing to the formation of protein carbonyl in HSA by tea catechins is the pyrogallol structural motif in the B-ring, followed by the galloyl group. By both mass spectrometry and electrophoresis/blotting with redox-cycling staining, we revealed that pyrogallol-type catechins had higher reactivity with protein thiols than catechol-type catechins.3.We synthesized[^<13> C]-ECg, in which the carbonyl carbon of the galloyl moiety was labeled by^<13> C isotope, and analyzed it by solid-state NMR spectroscopy. Solid-state^<31> P NMR analysis indicated that ECg changes the gel-to-liquid-crystalline phase transition temperature of DMPC bilayers as well as the dynamics and mobility of the phospholipids. The accurate intermolecular. interatomic distance between the labeled carbonyl carbon of[^<13> C]-ECg and the phosphorus of the phospholipid was determined to be 5.3±0.1 A by^<13> C.^<31> P rotational echo double resonance(REDOR) measurements.4.The DEAD-box RNA helicase p68, which is overexpressed in a variety of tumor cells and plays an important role in cancer development and progression, was identified as a novel EGCG-binding target.