The ability to specifically attach chemical probes to individual proteins represents a powerful approach to the study and manipulation of protein function in living cells. It provides a simple, robust and versatile approach to the imaging of fusion proteins in a wide range of experimental settings. However, a potential drawback of detection using chemical probes is the fluorescence background from unreacted or nonspecifically bound probes. In this report we present the design and application of novel fluorogenic probes for labeling SNAP-tag fusion proteins in living cells. SNAP-tag is an engineered variant of the human repair protein O6-alkylguanine-DNA alkyltransferase (hAGT) that covalently reacts with benzylguanine derivatives. Reporter groups attached to the benzyl moiety become covalently attached to the SNAP tag while the guanine acts as a leaving group. Incorporation of a quencher on the guanine group ensures that the benzylguanine probe becomes highly fluorescent only upon labeling of the SNAP-tag protein. We describe the use of intramolecularly quenched probes for wash-free labeling of cell surface-localized epidermal growth factor receptor (EGFR) fused to SNAP-tag and for direct quantification of SNAP-tagged β-tubulin in cell lysates. In addition, we have characterized a fast-labeling variant of SNAP-tag, termed SNAPf, which displays up to a tenfold increase in its reactivity towards benzylguanine substrates. The presented data demonstrate that the combination of SNAPf and the fluorogenic substrates greatly reduces the background fluorescence for labeling and imaging applications. This approach enables highly sensitive spatiotemporal investigation of protein dynamics in living cells.

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It is accepted that linear enamel hypoplasias (LEHs), a specific type of enamel thickness deficiency, are related to periodic physiological disruptions to enamel matrix secretion during times that teeth are developing. Thus, LEHs are treated as general indicators of metabolic stress. Because the disruptions that cause LEHs affect only the portion of the crown that is in the process of forming, determining their locations allows researchers to reconstruct chronologies of stressful events. It is widely held that the many of the commonly used macroscopic methods for estimating the timing of LEHs are imprecise and do not conform to our current understanding of the process of enamel formation. The goal of the present study is to compare estimated ages of LEH formation produced by two of the most commonly used macroscopic methods to those derived from data in recent histological studies that include more precise information about the timing of crown formation across diverse human populations. These approaches are compared in two ways: 1) by creating a theoretical model using simulated LEHs and 2) empirically, by analyzing data collected on a sample of ancient Nubians from Semna South (present-day Sudan). Results indicate that the approach derived from histological studies provides significantly higher age estimates than the commonly used methods and this difference is particularly marked in early forming LEHs. The magnitude of this difference is large enough to produce divergent interpretation of bioarchaeological datasets and suggests that reevaluation of the methods used to estimate ages of LEH formation may be justified.

Syphilis was perceived to be a new disease in Europe in the late 15th century, igniting a debate about its origin that continues today in anthropological, historical, and medical circles. We move beyond this age-old debate using an interdisciplinary approach that tackles broader questions to advance the understanding of treponemal infection (syphilis, yaws, bejel, and pinta). How did the causative organism(s) and humans co-evolve? How did the related diseases caused by Treponema pallidum emerge in different parts of the world and affect people across both time and space? How are T. pallidum subspecies related to the treponeme causing pinta? The current state of scholarship in specific areas is reviewed with recommendations made to stimulate future work. Understanding treponemal biology, genetic relationships, epidemiology, and clinical manifestations is crucial for vaccine development today and for investigating the distribution of infection in both modern and past populations.Paleopathologists must improve diagnostic criteria and use a standard approach for recording skeletal lesions on archaeological human remains. Adequate contextualization of cultural and environmental conditions is necessary, including site dating and justification for any corrections made for marine or freshwater reservoir effects. Biogeochemical analyses may assess aquatic contributions to diet, physiological changes arising from treponemal disease and its treatments (e.g., mercury), or residential mobility of those affected. Shifting the focus from point of origin to investigating who is affected (e.g., by age/sex or socioeconomic status) and disease distribution (e.g., coastal/ inland, rural/urban) will advance our understanding of the treponemal disease and its impact on people through time. K E Y W O R D S archaeological biogeochemistry,