The activity of Ixophilin might, in part, be instrumental in keeping the blood stored in the tick gut in a fluid state, and thus allow nutrient uptake by pinocytosis-an important aspect of blood meal digestion in ticks. Immunity against Ixophilin significantly delayed feeding time, and decreased engorgement weights, but did not abolish feeding. Interestingly, rIxophilin-immunized mice challenged with B. burgdorferi-infected nymphs, showed increased Borrelia burden in the murine host, although there was no impact on Borrelia burden in the nymphal guts and salivary glands. Presumably, the longer feeding period might have increased the window of time for pathogen transmission to occur. The tick gut may encode more than one anticoagulant that may compensate for loss of Ixophilin function, and allow feeding to proceed, and emphasizes the need to simultaneously target all predominant members of the anticoagulome to efficiently block tick feeding. Our observations suggest stage-specific and tissue-specific expression of Ixophilin, and underscore a critical role for the tick gut in keeping the blood meal fluid. Unlike the salivary anticoagulants, the gut-specific anticoagulants are not directly exposed to host immune pressure, and may not have evolved to circumvent host immune responses. The gut “anticoagulome” might therefore be a tractable subset, and could be targeted to disrupt tick feeding, and consequent pathogen transmission. The choice of MK-4827 detection technology is another critical aspect that must be determined with awareness of the limitations associated with each method, e.g. the inner filter effect for fluorescence technologies, high substrate conversion requirement for fluorescence polarization, interference with test compounds, detection limits, and the linear range of signal responses. In HTS for enzyme inhibitors a central concern is to design an assay with a high signal-to-background ratio, and to determine an observation window that provides appropriate separation in read-out between hits and the control samples. To achieve an assay with a good Z-factor, 
experimental noise should be minimized while maximizing the S/B ratio. A common experimental condition in HTS for enzyme inhibitors is to use low substrate concentrations to avoid saturation of the active site, which would risk missing competitive inhibitors. With low substrate concentrations it often becomes necessary to allow reactions to proceed until a large proportion of substrate becomes depleted in order to obtain sufficiently high signals. While such extended incubation times may obscure the effect of weak inhibitors, shorter incubation times give weaker signals that may adversely affect assay performance. Different modes of inhibition further complicates data WZ4002 interpretation and assay design. A further difficulty is that the underlying theory, which is based on rate-law equations for initial reaction velocity, becomes violated at extended reaction times and thus complicates data interpretation, particularly the relation between observed and true inhibitor potency. In experimental deduction of kinetic parameters, the initial reaction rate at different substrate concentrations is measured and data obtained fitted to the Michaelis-Menten rate law equation. In practice, initial reaction rates can only be approximated since the real measurable quantity represents a concentration at a given time-point.