1:1 cyclic compounds 8a-c (51-55%) and 2:2 cyclic compounds 9a-c (20-49%) containing 1,4,7,10-tetraazacyclododecane (cyclen) and azobenzene units were selectively synthesized under UV irradiation (330 nm < lambda < 380 nm) and in the dark. Synthesis depended on the wavelength of irradiation light and the length of methylene chains of the linker between the cyclen and azobenzene units. A study of NMR and UV-vis spectra indicated that properties of 8a-c and 9a-c are closely related to their structural flexibility. Rate constants (k) and thermodynamic parameters (DeltaG(), DeltaH(), and DeltaS()) of 8a-c and 9a-c were studied in nonpolar media (benzene) and polar media (methanol). The cis to trans isomerization rates in the dark for these cyclic compounds increase with ring size or structural flexibility (8a < 8c < 8b < 9a < 9b < 9c). In principle, DeltaS() dominates DeltaG() in cyclic compounds.

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Detection of people with acute HIV infection (AHI) affords an important opportunity for early HIV treatment and prevention. HIV RNA reverse transcriptase-polymerase chain reaction (RT-PCR) testing with two-stage pooling scheme was used to detect the AHI in specimens collected from sexually transmitted disease (STD) clinic patients in Guangxi, China. A total of 246 HIV RNA tests were required to screen 11 395 samples negative for conventional enzyme immunoassay (EIA) and Western blot assays, and five AHI cases (0.04%, 95%CI 0.02% to 0.10%) with a high viral load (median of 265,677 copies per ml) were detected. The total expenditure for RT-PCR testing reflected an added cost of $2.9 per specimen screened and $6575 per additional case of AHI identified among the study population. This study supports the feasibility of pooled RNA testing in addition to detection of HIV infections among patients at STD clinics in China, but the cost effectiveness should be carefully considered.