  Correlation functions of chiral primary operators and their superconformal
descendants in the N=4 supersymmetric SU(N) Yang-Mills theory are studied in
detail in a one-instanton background and at large N. Whereas earlier
calculations were restricted to correlation functions that are saturated by the
16 exact superconformal fermionic moduli, here the effect of the set of
additional fermionic moduli associated with the embeddings of the SU(2)
instanton in SU(N) is considered. The presence of the extra fermionic modes is
essential for matching Yang-Mills instanton effects in various correlation
functions with D-instanton effects in type IIB string theory via the AdS/CFT
conjecture. The leading terms of this kind on the string side contribute at
order 1/(alpha'), which is the same order as the R^4 interaction. For example,
the instanton contributions to correlation functions of higher dimensional
chiral primary operators are seen to match amplitudes involving Kaluza-Klein
excitations of the supergravity fields, as expected. Another example is the
matching of certain multi-fermion correlation functions which correspond to
certain multi-fermion interactions required by supersymmetry of the IIB string
effective action. Careful analysis of a variety of competing effects makes it
possible to decipher contributions corresponding to higher derivative
interactions in the IIB effective action. In this manner it is possible to
check for the presence of terms of order alpha'. Comments are also made on the
structure of instanton contributions to near-extremal correlation functions of
chiral primary operators.
