One of the most important current scientific paradoxes is the economy with which nature uses genes. In all higher animals studied, we have found many fewer genes than we would have previously expected. The functional outputs of the eventual products of genes seem to be far more complex than the more restricted blueprint. In higher organisms, the functions of many proteins are modulated by post-translational modifications (PTMs). These alterations of amino-acid side chains lead to higher structural and functional protein diversity and are, therefore, a leading contender for an explanation for this seeming incongruity. Natural protein production methods typically produce PTM mixtures within which function is difficult to dissect or control. Until now it has not been possible to access pure mimics of complex PTMs. Here we report a chemical tagging approach that enables the attachment of multiple modifications to bacterially expressed (bare) protein scaffolds: this approach allows reconstitution of functionally effective mimics of higher organism PTMs. By attaching appropriate modifications at suitable distances in the widely-used LacZ reporter enzyme scaffold, we created protein probes that included sensitive systems for detection of mammalian brain inflammation and disease. Through target synthesis of the desired modification, chemistry provides a structural precision and an ability to retool with a chosen PTM in a manner not available to other approaches. In this way, combining chemical control of PTM with readily available protein scaffolds provides a systematic platform for creating probes of protein-PTM interactions. We therefore anticipate that this ability to build model systems will allow some of this gene product complexity to be dissected, with the aim of eventually being able to completely duplicate the patterns of a particular protein's PTMs from an in vivo assay into an in vitro system.

A multiconfiguration self-consistent reaction field linear response method is presented for calculating frequency-dependent molecular properties as well as electronic excitation energies and transition moments of solvated molecules. Sample calculations are presented of a solvated water molecule and show a substantial dependence on the properties of the surrounding solvent. The solvent effect cannot be described as a correction to the vacuum value involving simple scalar factors.

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Relativistic four-component random phase approximation ͑RPA͒ calculations of indirect nuclear spin-spin coupling constants in MH 4 (MϭC, Si, Ge, Sn, Pb) and Pb͑CH 3 ͒ 3 H are presented. The need for tight s-functions also in relativistic four-component calculations is verified and explained, and the effect of omission of ͑SS-LL͒ and ͑SS-SS͒ two-electron integrals is investigated. Already in GeH 4 we see a relativistic increase in the coupling constant by 12%, and for PbH 4 the effect is a 156% increase for the one-bond coupling. Large relativistic effects are also computed for the two-bonds couplings. We find that the relativistic effects on the one-bond couplings are mainly due to scalar relativistic factors rather than spin-orbit corrections.

A tetrafluoro-substituted fluorescein derivative covalently linked to a 9,10-diphenyl anthracene moiety has been synthesized, and its photophysical properties have been characterized. This compound, denoted Aarhus Sensor Green (ASG), has distinct advantages for use as a fluorescent probe for singlet molecular oxygen, O2(a(1)Δg). In the least, ASG overcomes several limitations inherent to the use of the related commercially available product called Singlet Oxygen Sensor Green (SOSG). The functional behavior of both ASG and SOSG derives from the fact that these weakly fluorescent compounds rapidly react with singlet oxygen via a π2 + π4 cycloaddition to irreversibly yield a highly fluorescent endoperoxide. The principal advantage of ASG over SOSG is that, at physiological pH values, both ASG and the ASG endoperoxide (ASG-EP) do not themselves photosensitize the production of singlet oxygen. As such, ASG better fits the requirement of being a benign probe. Although ASG readily enters a mammalian cell (i.e., HeLa) and responds to the presence of intracellular singlet oxygen, its behavior in this arguably complicated environment requires further investigation.