CL:  From that paper there are 2 forms of neonics.  That right there is a huge mental step,  as I assumed the term neonics was type specific.  So I am to understand they also have different modes of action??  

CW:  Neonicotinoids get their names (are classified) according to what they do...they bind to the acetylcholine receptor in nerve synapses.  The basic mode of action is the same for all of them.  

 CL:  What makes them different,  the way the work, or how they were made or???  

CW:  They work just like keys.  Keys can have different shapes and still fit the same lock.  Same thing with these compounds....they can (and do) have different atomic arrangements and shapes...that makes them chemically different.  But the important part of their shape....the part that fits the lock....varies only a little.  So, all of them can block the acetylcholine receptor open.

CL:  Then the question would be do they have the same properties?  It seems at least the metabolic rates are different??  

CW:  They have different binding affinities to the receptor....some of them are very highly toxic and others less so (dosage for same effect varies).  And because their shapes and molecular formulas differ, except at the binding site,  these authors have shown that they are metabolized (broken down) differently.  They have identified at least two different breakdown pathways for two major neonic "types"....and both types are in common use.   

The body mostly uses enzymes to break down compounds.  The function of enzymes, like the function of the acetylcholine receptor, is highly shape-specific.  If the breakdown enzyme(s) cannot "grab" the neonic because the shapes don't fit, then it cannot help to catalyze a reaction that might otherwise begin to degrade and ultimately deactivate it.  In this paper, the two classes of neonics that the authors describe are broken down by different mechanisms.  One of those mechanisms is interfered with by a common fungicide, and the consequence is that the neonic breaks down even more slowly than usual (which is already pretty slow since as we have seen, a critically small amount is trapped in tissue "sinks" like synapses to cause lengthy depolarization trouble).

So that's why I think it would be interesting to know what the seed coat formulations are, and what kind of field applications are typical for different crops.  

I suspect that Bayer and the rest know all this very well and have taken care not to mix fungicides with cyano-substituted neonics.  But it would be nice to check on that.  Different mixes are coating different crop seeds.  And also it would be good to know whether farmers spray or otherwise apply additional stuff (like fungicides) later, while the neonics are still actively present in the plants.

Christina


    
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