Elements subclassifications

Although all transposons with a DDE transposase ( DDE transposons ) use this type of chemistry, a large diversity exists in the overall transposition mechanism. As explained above, DDE transposases catalyze only single-strand cleavage and transfer of the 3 -OH transposon ends (the transferred strand). However, to liberate the transposable element from donor DNA, the transposase must deal with the second DNA strand (also called the nontransferred strand (3, 24). A subclassification of DDE transposons is based on the mechanisms used to manage this. 

Humic and fulvic acids are presumed to arise by two classical natural processes. Terrestrial humates are found in the following pathway plants soil humates peat — coal. Aquatic humates start with soil leachates or marine phytoplankton and go through a sequence sediments kerogen petroleum. There are conditions which mix the two processes as well. As a result, there are a host of names and symbols applied to these compounds, such as peat humic acid, coal fulvic acid, soil humic acid, and so on. Depending on their oxidation state, they may be heavily bound to metal ions. Within each class of humic acid, there are subclassifications, such as Podzol Bj, humic acid, lignite fulvic acid. Other types are classified by geological age, depth in a sediment, and type of aquatic environment. The following discussion will attempt to relate elemental composition to these broad classes of humates. 

We mentioned in Section 1.3 that chemists simplify the task of studying the enormous quantity of different material substances that exist by placing them into classifications and subclassifications. Let us now take another look at the periodic table and see what subclassifications chemists have used for the elements. 

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