Bioconjugation of Green Fluorescent Protein via an Unexpectedly Stable Cyclic Sulfonium Intermediate

Bioconjugation of superfolder GFP involving the formation of an unusually stable, and unprecedented, cyclic sulfonium species is described. This sulfonium can undergo smooth reaction with a range of nucleophiles to give sulfur-, selenium- and azide-modified GFP derivatives in high conversions

Liverpool Telescope Technical Note 1: Telescope and IO:O Throughput

We measure the absolute photon efficiency of the Liverpool Telescope using observations of photometric standard stars and a throughput model of the IO:O instrument. Over a period of 1 year following mirror re-coating the telescope transmission is in the range 73-79% over 4000-10000 Angstroms. Transmission in the u'-band (~3500 Angstroms) is slightly lower at 65%. Immediately following mirror re-coating the throughput is shown to be consistent within 4% to predictions for two reflections from bare-aluminium-coated optics. The telescope throughput (two reflections) degrades at a rate ~0.0002 mag/day. Also presented are the effective wavelengths and widths for the u',g',r',i',z',B,V broad-band filters, taking into account all optical components of the system

Tests of additional conditional moment restrictions

© 2017 Elsevier B.V. The primary focus of this article is the provision of tests for the validity of a set of conditional moment constraints additional to those defining the maintained hypothesis that are relevant for independent cross-sectional data contexts. The point of departure and principal contribution of the paper is the explicit and full incorporation of the conditional moment information defining the maintained hypothesis in the design of the test statistics. Thus, the approach mirrors that of the classical parametric likelihood setting by defining restricted tests in contradistinction to unrestricted tests that partially or completely fail to incorporate the maintained information in their formulation. The framework is quite general allowing the parameters defining the additional and maintained conditional moment restrictions to differ and permitting the conditioning variates to differ likewise. GMM and generalised empirical likelihood test statistics are suggested. The asymptotic properties of the statistics are described under both null hypothesis and a suitable sequence of local alternatives. An extensive set of simulation experiments explores the practical efficacy of the various test statistics in terms of empirical size and size-adjusted power confirming the superiority of restricted over unrestricted tests. A number of restricted tests possess both sufficiently satisfactory empirical size and power characteristics to allow their recommendation for econometric practice

Photodissociation and the Morphology of HI in Galaxies

Young massive stars produce Far-UV photons which dissociate the molecular gas on the surfaces of their parent molecular clouds. Of the many dissociation products which result from this ``back-reaction'', atomic hydrogen \HI is one of the easiest to observe through its radio 21-cm hyperfine line emission. In this paper I first review the physics of this process and describe a simplified model which has been developed to permit an approximate computation of the column density of photodissociated \HI which appears on the surfaces of molecular clouds. I then review several features of the \HI morphology of galaxies on a variety of length scales and describe how photodissociation might account for some of these observations. Finally, I discuss several consequences which follow if this view of the origin of HI in galaxies continues to be successful.Comment: 18 pages, 7 figures in 8 files, invited review paper for the conference "Penetrating Bars Through Masks of Cosmic Dust: The Hubble Tuning Fork Strikes a New Note", South Africa, June 2004. Proceedings to be published by Kluwer, eds. D.L. Block, K.C. Freeman, I. Puerari, R. Groess, & E.K. Bloc

Expressions for forces and torques in molecular simulations using rigid bodies

Expressions for intermolecular forces and torques, derived from pair potentials between rigid non-spherical units, are presented. The aim is to give compact and clear expressions, which are easily generalised, and which minimise the risk of error in writing molecular dynamics simulation programs. It is anticipated that these expressions will be useful in the simulation of liquid crystalline systems, and in coarse-grained modelling of macromolecules

Simultaneous detection of positive and negative secondary ions

A secondary ion mass spectrometer (SIMS) instrument is described that is configured with two SIMSdetectors that are both low-field extraction, quadrupole-based filters. Secondary ions are generated by sputtering with a liquid-metal ion gallium source and column of the type that is common on two-beam electron microscopes. The gallium ion beam, or focused ion beam achieves sub-100 nm focus with a continuous current of up to 300 pA. Positive secondary ions are detected by one SIMSdetector, and simultaneously, negative secondary ions are detected by the second SIMSdetector. The SIMSdetectors are independently controlled for recording mass spectra, concentration depth profiles, and secondary ion images. Examples of simultaneous positive and negative SIMS are included that demonstrate the advantage of this facility for surface analysis and depth profiling. The SIMS secondary ion collection has been modeled using the ray tracing program simion (“simion”, Scientific Instrument Services, Inc., Ringoes, NJ, 08551-1054, see http://www.simion.com) in order to understand the interaction of the secondary ions of opposite polarities in the extraction volume for the purpose of optimizing secondary ion collection

T cell growth factor receptors. Quantitation, specificity, and biological relevance

To examine directly the hypothesis that T cell growth factor (TCGF) interacts with target cells in a fashion similar to polypeptide hormones, the binding of radiolabeled TCGF to various cell populations was investigated. The results indicate that TCGF interacts with activated T cells via a receptor through which it initiates the T cell proliferative response. Internally radiolabeled TCGF, prepared from a human T leukemia cell line and purified by gel filtration and isoelectric focusing, retained biological activity and was uniform with respect to size and charge. Binding of radiolabeled TCGF to TCGF-dependent cytolytic T cells occurred rapidly (within 15 rain at 37 degrees C) and was both saturable and largely reversible. In addition, at 37 degrees C, a receptor- and lysosome-dependent degradation of TCGF occurred. Radiolabeled TCGF binding was specific for activated, TCGF-responsive T cells. Whereas unstimulated lymphocytes of human or murine origin and lipopolysaccharide-activated B cell blasts expressed few if any detectable binding sites, lectin- or alloantigen-activated cells had easily detectable binding sites. Moreover, compared with lectin- or alloantigen-activated T cells, long-term TCGF-dependent cytolytic and helper T cell lines and TCGF-dependent neo-plastic T cell lines bound TCGF with a similar affinity (dissociation constant of 5-25 pM) and expressed a similar number of receptor sites per cell (5,000-15,000). In contrast, a number of TCGF-independent cell lines of T cell, B cell, or myeloid origin did not bind detectable quantities of radiolabeled TCGF. Binding of radiolabeled TCGF to TCGF-responsive cells was specific, in that among several growth factors and polypeptide hormones tested, only TCGF competed for binding. Finally, the relative magnitude of T cell proliferation induced by a given concentration of TCGF closely paralleled the fraction of occupied receptor sites. As the extent of T cell clonal expansion depends on TCGF and on the TCGF receptor, the dissection of the molecular events surrounding the interaction of TCGF and its receptor that these studies permit, should provide new insight into the hormonelike regulation of the immune response by this lymphokine

The HadGEM3-GA7.1 radiative kernel: the importance of a well-resolved stratosphere

We present top-of-atmosphere and surface radiative kernels based on the atmospheric component (GA7.1) of the HadGEM3 general circulation model developed by the UK Met Office. We show that the utility of radiative kernels for forcing adjustments in idealised CO2 perturbation experiments is greatest where there is sufficiently high resolution in the stratosphere in both the target climate model and the radiative kernel. This is because stratospheric cooling to a CO2 perturbation continues to increase with height, and low-resolution or low-top kernels or climate model output are unable to fully resolve the full stratospheric temperature adjustment. In the sixth phase of the Coupled Model Intercomparison Project (CMIP6), standard atmospheric model data are available up to 1 hPa on 19 pressure levels, which is a substantial advantage compared to CMIP5. We show in the IPSL-CM6A-LR model where a full set of climate diagnostics are available that the HadGEM3-GA7.1 kernel exhibits linear behaviour and the residual error term is small, as well as from a survey of kernels available in the literature that in general low-top radiative kernels underestimate the stratospheric temperature response. The HadGEM3-GA7.1 radiative kernels are available at https://doi.org/10.5281/zenodo.3594673 (Smith, 2019)

Towns in victorian England and Wales: A new classification

ABSTRACT:This article describes the creation of a new urban classification based on the 1891 census of England and Wales. It is the first attempt to use the recently available electronic version of the census (I-CeM) to classify all large towns in late Victorian England and Wales on their economic structure. Where previous scholars were restricted by the form of occupation data contained in the published census reports, I-CeM allows manipulation of the data in order to aggregate urban units and examine their occupational structures in great detail. The classification is then used to compare key socio-economic characteristics of different towns.</jats:p