According to Dr. Robert Fowler, when is it most likely that Hughes' fear for his own well-being developed?

The underlying cause of germ phobia is thought to be related to negative experiences, genetics, environment, and changes in brain functioning, or a combination of those factors. Two years after Howard Hughes’s death, Dr. Raymond Fowler conducted a psychological autopsy in an attempt to understand the cause of his disorder and when it began. After a comprehensive investigation into the life of Hughes, Fowler believed the condition developed in his childhood. Hughes was an isolated child with no friends. His mother kept him away from other children because she believed they were all infested with germs. She also constantly worried about his exposure to germs and was terrified he would become sick. She checked him for diseases every day and closely monitored everything he ate.

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enzyme active site and substrate specificity

enzymes bind with chemical reactants called substrates. there may be one or more substrates for each type of enzyme, depending on the particular chemical reaction. in some reactions, a single-reactant substrate is broken down into multiple products