Design and synthesis of a multivalent catch-and-release assay to measure circulating FXIa.

BACKGROUND: Decreased blood coagulation factor (F)XIa levels have been shown to protect from thrombosis without bleeding side effects, but less is known on effects of increased FXIa levels. Studies are hampered by lack of a reliable and robust method for FXIa quantification in blood. We aim to develop a new assay employing a unique multivalent catch-and-release system. The system selectively isolates and protects homodimeric FXIa from plasma and releases free FXIa allowing subsequent quantification. METHODS: A dynamic multivalent construct was synthesized by complexing four identical FXIa inhibitors from the snake Bungarus Fasxiatus to avidin through desthiobiotin-PEG-linkers, allowing dissociation of FXIa by excess biotin. PEG-linker lengths were optimised for FXIa inhibitory activity and analysed by Michaelis-Menten kinetics. Finally, the catch-and-release assay was validated in buffer and plasma model systems. RESULTS: Monovalent and multivalent inhibitor constructs were successfully obtained by total chemical synthesis. Multimerisation of Fasxiator resulted in a 30-fold increase in affinity for FXIa from 1.6 nM to 0.05 nM. With use of this system, FXIa could be quantified down to a concentration of 7 pM in buffer and 20 pM in plasma. CONCLUSION: In this proof-of-concept study, we have shown that the catch-and-release approach is a promising technique to quantify FXIa in plasma or buffer. By binding FXIa to the multivalent construct directly after blood drawing, FXIa is hypothesized to be inaccessible for serpin inhibition or auto inactivation. This results in a close reflection of actual circulating FXIa levels at the moment of blood drawing.

[Maternal bonding and a healthy life style during pregnancy]. / Materské pouto a zdravý zivotní styl v tehotenství.

Maternal bonding in pregnancy appears to be an important factor, which may influence psychical and physical development of the child both before and after the birth. One of the significant determining factors of such influence is change in the general life style of the pregnant woman, which correspond with the strength of the maternal bonding. The study brings information on the basis of an empirical research, which was done, in ninetieths at a Research Institute of the Child Health in Brno. The investigated group comprised of 481 pregnant women who were all living in Brno. Results of our research bring the information about relations between the strength of maternal bonding and occupational position of the pregnant women, intensity of working activities and the way of spending their leisure time. Beside it, out research informs about some health risk activities in pregnancy and their relations to the formation of the emotional bonding towards unborn child.