Structure-Dependent Mechanism of Organophosphate Release from Albumin and Butyrylcholinesterase Adducts When Exposed to Fluoride Ion: A Comprehensive In Silico Study.

The most favorable targets for retrospectively determining human exposure to organophosphorus pesticides, insecticides, retardants, and other industrial organophosphates (OPs) are adducts of OPs with blood plasma butyrylcholinesterase (BChE) and human serum albumin (HSA). One of the methods for determining OP exposure is the reactivation of modified BChE using a concentrated solution of KF in an acidic medium. It is known that under the action of fluoride ion, OPs or their fluoroanhydrides can be released not only from BChE adducts but also from the adducts with albumin; however, the contribution of albumin to the total pool of released OPs after plasma treatment with KF has not yet been studied. The efficiency of OP release can be affected by many factors associated with the experimental technique, but first, the structure of the adduct must be taken into account. We report a comparative analysis of the structure and conformation of organophosphorus adducts on HSA and BChE using molecular modeling methods and the mechanism of OP release after fluoride ion exposure. The conformational analysis of the organophosphorus adducts on HSA and BChE was performed, and the interaction of fluoride ions with modified proteins was studied by molecular dynamics simulation. The geometric and energy characteristics of the studied adducts and their complexes with fluoride ion were calculated using molecular mechanics and semiempirical approaches. The structural features of modified HSA and BChE that can affect the efficiency of OP release after fluoride ion exposure were revealed. Using the proposed approach, the expediency of using KF for establishing exposure to different OPs, depending on their structure, can be assessed.

Determination of fluoroacetic acid in water and biological samples by GC-FID and GC-MS in combination with solid-phase microextraction.

A novel procedure has been developed for determination of fluoroacetic acid (FAA) in water and biological samples. It involves ethylation of FAA with ethanol in the presence of sulfuric acid, solid-phase microextraction of the ethyl fluoroacetate formed, and subsequent analysis by GC-FID or by GC-MS in selected-ion-monitoring mode. The detection limits for FAA in water, blood plasma, and organ homogenates are 0.001 microg mL(-1), 0.01 microg mL(-1), and 0.01 microg g(-1), respectively. The determination error at concentrations close to the detection limit was less than 50%. For analysis of biological samples, the approach has the advantages of overcoming the matrix effect and protecting the GC and GC-MS systems from contamination. Application of the approach to determination of FAA in blood plasma and organ tissues of animals poisoned with sodium fluoroacetate reveals substantial differences between the dynamics of FAA accumulation and clearance in rabbits and rats.