write:3. Since triisopropylsilyl groups is new and important information here create for it a stressposition. 4. Triisopropylsilyl groups then becomes the old information of the clause

keep them up front in thetopic position. 3.Since triisopropylsilyl groups is new and important information here
create for it a stressposition. 4.Triisopropylsilyl groups then becomes the old information of the clause in which its effects aredescribed; place it in the topic position of this clause. 5.Alert the reader to expect the arrival of two distinct effects by using the flag word both. Bothnotifies the reader that two pieces of new information will arrive in a single stress position. Here is a partial revision based on these decisions: We have directly measured the enthalpy of hydrogen bond formation between the nucleoside bases2’deoxyguanosine (dG) and 2’deoxycytidine (dC). dG and dC were derivatized at the 5’ and 3’hydroxyls with triisopropylsilyl groups; these groups serve both to solubilize the nucleosides innon-aqueous solvents and to prevent the ribose hydroxyls from forming hydrogen bonds. Fromisoperibolic titration measurements
the enthalpy of dC:dG base pair formation is -6.65±0.32kcal/mol. The outlines of the experiment are now becoming visible
but there is still a major logical gap. Afterreading the second sentence
we expect to hear more about the two effects that were important enough tomerit placement in its stress position. Our expectations are frustrated
however
when those effects arenot mentioned in the next sentence: From isoperibolic titration measurements
the enthalpy of dC:dGbase pair formation is -6.65±0.32 kcal/mol. The authors have neglected to explain the relationshipbetween the derivatization they performed (in the second sentence) and the measurements they made (inthe third sentence). Ironically
that is the point they most wished to make here. At this juncture
particularly astute readers who are chemists might draw upon their specializedknowledge
silently supplying the missing connection. Other readers are left in the dark. Here is oneversion of what we think the authors meant to say
with two additional sentences supplied from aknowledge of nucleic acid chemistry: We have directly measured the enthalpy of hydrogen bond formation between the nucleoside bases2’deoxyguanosine (dG) and 2’deoxycytidine (dC). dG and dC were derivatized at the 5’ and 3’hydroxyls with triisopropylsiyl groups; these groups serve both to solubilize the nucleosides innon-aqueous solvents and to prevent the ribose hydroxyls from forming hydrogen bonds.Consequently
when the derivatized nucleosides are dissolved in non-aqueous solvents
hydrogenbonds form almost exclusively between the bases. Since the interbase hydrogen bonds are the onlybonds to form upon mixing
their enthalpy of formation can be determined directly by measuringthe enthalpy of mixing. From our isoperibolic titration measurements
the enthalpy of dG:dC basepair formation is -6.65±0.32 kcal/mol. Each sentence now proceeds logically from its predecessor. We never have to wander too far into asentence without being told where we are and what former strands of discourse are being continued.And the measurements of the last sentence has now become old information
reaching back to themeasured directly of the preceding sentence. (It also fulfills the promise of the we have directlymeasured with which the paragraph began.) By following our knowledge of reader expectations
we