The Potential Energy Surface in Molecular Quantum Mechanics

The idea of a Potential Energy Surface (PES) forms the basis of almost all accounts of the mechanisms of chemical reactions, and much of theoretical molecular spectroscopy. It is assumed that, in principle, the PES can be calculated by means of clamped-nuclei electronic structure calculations based upon the Schr\"{o}dinger Coulomb Hamiltonian. This article is devoted to a discussion of the origin of the idea, its development in the context of the Old Quantum Theory, and its present status in the quantum mechanics of molecules. It is argued that its present status must be regarded as uncertain.Comment: 18 pages, Proceedings of QSCP-XVII, Turku, Finland 201

Persistent and Selective Deficiency of CD4+ T Cell Immunity to Cytomegalovirus in Immunocompetent Young Children

Healthy young children who acquire CMV have prolonged viral shedding into the urine and saliva, but whether this is attributable to limitations in viral-specific immune responses has not been explored. In this study, we found that otherwise immunocompetent young children after recent primary CMV infection accumulated markedly fewer CMV-specific CD4+ T cells that produced IFN-γ than did adults. These differences in CD4+ T cell function persisted for more than 1 year after viral acquisition, and did not apply to CMV-specific IFN-γ production by CD8+ T cells. The IFN-γ-producing CD4+ T cells of children or adults that were reactive with CMV Ags were mainly the CCR7low cell subset of memory (CD45R0highCD45RAlow) cells. The decreased IFN-γ response to CMV in children was selective, because their CCR7 low memory CD4+ T cells and those of adults produced similar levels of this cytokine after stimulation with staphylococcal enterotoxin B superantigen. CD4+ T cells from children also had reduced CMV-specific IL-2 and CD154 (CD40 ligand) expression, suggesting an early blockade in the differentiation of viral-specific CD4+ T cells. Following CMV acquisition, children, but not adults, persistently shed virus in urine, and this was observable for at least 29 mo postinfection. Thus, CD4+ T cell-mediated immunity to CMV in humans is generated in an age-dependent manner, and may have a substantial role in controlling renal viral replication and urinary shedding.link_to_subscribed_fulltex

Antiviral CD8 T cells in the control of primary human cytomegalovirus infection in early childhood

Human cytomegalovirus (CMV) establishes persistent infection, with control of replication thought to be mediated by CMV-specific CD8 T cells. Primary CMV infection commonly affects young children and causes prolonged viral shedding in saliva and urine. We investigated whether this virus-host interaction pattern reflects a developmental deficiency of antiviral CD8 T cell-mediated immunity during childhood. CMV-specific CD8 T cell responses in asymptomatic children with active infection were not different from adults with recent or long-term infection in frequency and functional analyses. High urine CMV concentrations were detected, despite these CMV-specific CD8 T cell responses. We conclude that delayed resolution of primary CMV infection in young children is not caused by a deficient CMV-specific CD8 T cell response. Because these healthy children continue to have local CMV replication, we suggest that CD8 T cells may function primarily to prevent symptomatic, disseminated disease.link_to_subscribed_fulltex