Browsing by Author "Schwarz, Benjamin"

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Enzyme encapsulation in the P22 viral capsid as a platform for biological nanoreactors
(2013-03) Schwarz, Benjamin; Douglas, Trevor
The capsid of the Salmonella typhimurium bacteriophage P22 presents a platform for encapsidation of protein cargo through genetic fusion. The capsid spontaneously assembles via interactions between a scaffold protein and the interior of the coat protein shell. By fusing proteins to a truncated scaffold protein it is possible to package cargo inside the capsid which has potential to generate thermostable, dynamic, targetable nanoreactors. The present work proves this concept with the encapsidation of two thermophilic enzymes, the monomeric alcohol dehydrogenase AdhD and the tetrameric β;-glucosidase CelB both from Pyrococcus furiousus. Both enzymes are shown to be active in the packaged form and present within the capsid in large numbers, 85 monomers /capsid in CelB and 250 monomers/capsid in AdhD. The functionalized capsids were shown to retain the temperature dependent maturation seen in the wild type.
Reanalysis of Polythermal Glacier Thermal Structure Using Radar Diffraction Focusing
(American Geophysical Union, 2022-01) Delf, Richard; Bingham, Robert G.; Curtis, Andrew; Singh, Satyan; Giannopoulos, Antonios; Schwarz, Benjamin; Borstad, Chris P.
Ground-penetrating radar (GPR) is widely used on polythermal glaciers to image bed topography and detect internal scatter due to water inclusions in temperate ice. The glaciological importance of this is twofold: bed topography is a primary component for modeling the long-term evolution of glaciers and ice sheets, and the presence of temperate ice and associated englacial water significantly reduces overall ice viscosity. Englacial water has a direct influence on radar velocity, which can result in incorrect observations of bed topography due to errors in depth conversion. Assessment of radar velocities often requires multi-offset surveys, yet these are logistically challenging and time consuming to acquire, hence techniques to extract velocity from common-offset data are required. We calculate englacial radar velocity from common offset GPR data collected on Von Postbreen, a polythermal glacier in Svalbard. We first separate and enhance the diffracted wavefield by systematically assessing data coherence. We then use the focusing metric of negative entropy to deduce a migration velocity field and produce a velocity model which varies spatially across the glacier. We show that this velocity field successfully differentiates between areas of cold and temperate ice and can detect lateral variations in radar velocity close to the glacier bed. This velocity field results in consistently lower ice depths relative to those derived from a commonly assumed constant velocity, with an average difference of 4.9 ± 2.5% of local ice depth. This indicates that diffraction focusing and velocity estimation are crucial in retrieving correct bed topography in the presence of temperate ice.
Structural characterization of amphiphilic siderophores produced by a soda lake isolate, Halomonas sp. SL01, reveals cysteine-, phenylalanine- and proline-containing head groups
(2015-11) Figueroa, L. O.; Schwarz, Benjamin; Richards, Abigail M.
Soap Lake, located in Washington state, is a naturally occurring saline and alkaline lake. Several organisms inhabiting this lake have been identified as producers of siderophores that are unique in structure. Bacterial isolates, enriched from Soap Lake sediment and water samples, were screened for siderophore production using both the chrome azurol S (CAS) agar plate and liquid methods. Bacterial isolate Halomonas sp. SL01 was found to produce relatively high concentrations of siderophores in liquid medium (up to 40 ÂµM). Siderophores from the isolate were separated from the culture supernatant using solid phase extraction and purified by high-performance liquid chromatography (HPLC). Siderophore structure was determined using LC/MS/MS (liquid chromatography/mass spectrometry/mass spectrometry) and fatty acid methyl ester (FAME) GC. Two distinct new families of amphiphilic siderophores were produced by isolate SL01. All siderophores ranged in size from 989 to 1096 atomic mass units and consisted of a conserved peptidic head group (per family), which coordinates iron, coupled to fatty acid moieties. The fatty acyl moieties were C10â€“C14 in length and some with hydroxyl substitutions at the third Î± position. These siderophores resembled amphiphilic aquachelin siderophores produced by Halomonas aquamarina strain DS40M3, a marine bacterium as well as siderophores from isolate Halomonas sp. SL28 that was found to produce amphiphilic siderophores. Bacteria thriving under saline and alkaline conditions are capable of producing unique siderophores resembling those produced by microbes inhabiting marine environments.