X-ray free-electron lasers provide novel opportunities to conduct single particle analysis on nanoscale particles. Coherent diffractive imaging experiments were performed at the Linac Coherent Light Source (LCLS), SLAC National Laboratory, exposing single inorganic core-shell nanoparticles to femtosecond hard-X-ray pulses. Each facetted nanoparticle consisted of a crystalline gold core and a differently shaped palladium shell. Scattered intensities were observed up to about 7 nm resolution. Analysis of the scattering patterns revealed the size distribution of the samples, which is consistent with that obtained from direct real-space imaging by electron microscopy. Scattering patterns resulting from single particles were selected and compiled into a dataset which can be valuable for algorithm developments in single particle scattering research.

Viral protein U (Vpu) is a type-III integral membrane protein encoded by Human Immunodeficiency Virus-1 (HIV- 1). It is expressed in infected host cells and plays several roles in viral progeny escape from infected cells, including down-regulation of CD4 receptors. But key structure/function questions remain regarding the mechanisms by which the Vpu protein contributes to HIV-1 pathogenesis. Here we describe expression of Vpu in bacteria, its purification and characterization. We report the successful expression of PelB-Vpu in Escherichia coli using the leader peptide pectate lyase B (PelB) from Erwinia carotovora. The protein was detergent extractable and could be isolated in a very pure form. We demonstrate that the PelB signal peptide successfully targets Vpu to the cell membranes and inserts it as a type I membrane protein. PelB-Vpu was biophysically characterized by circular dichroism and dynamic light scattering experiments and was shown to be an excellent candidate for elucidating structural models.

Animals use diverse signal types (e.g. visual, auditory) to honestly advertise their genotypic and/or phenotypic quality to prospective mates or rivals. Behavioral displays and other dynamically updateable signals (e.g. songs, vibrations) can reliably reveal an individual’s quality in real-time, but it is unclear whether more fixed traits like feather coloration, which is often developed months before breeding, still reveal an individual’s quality at the time of signal use. To address this gap, we investigated if various indices of health and condition – including body condition (residual body mass), poxvirus infection, degree of habitat urbanization, and circulating levels of ketones, glucose, vitamins, and carotenoids – were related to the expression of male plumage coloration at the start of the spring breeding season in wild male house finches (Haemorhous mexicanus), a species in which many studies have demonstrated a link between plumage redness and the health and condition of individuals at the time the feathers are grown in late summer and autumn. We found that, at the time of pair formation, plumage hue was correlated with body condition, such that redder males were in better condition (i.e. higher residual mass). Also, as in previous studies, we found that rural males had redder plumage; however, urban males had more saturated plumage. In sum, these results reveal that feather coloration developed long before breeding still can be indicative to choosy mates of a male’s current condition and suggest that females who prefer to mate with redder males may also gain proximate material benefits (e.g. better incubation provisioning) by mating with these individuals in good current condition.

Bioindicators of wildlife health are useful tools for studying the viability of various organisms and populations, and can include a range of phenotypic variables, such as behavior, body size, and physiological parameters, such as circulating hormones and nutrients. Few studies have investigated the utility of total plasma protein as a predictor of environmental or nutritional variation among birds, as well as variation across different seasons and life-history stages. Here I examined relationships between plasma protein and season, urbanization, sex, body condition, molt status, and disease state in house finches (Haemorhous mexicanus). I sampled blood from house finches across three seasons (winter, summer and fall 2021) and measured plasma protein levels using a Bradford assay. I also collected data including condition, sex, and poxvirus infection state at capture, as well as fecal samples to assess gut parasitism (coccidiosis). During the fall season I also estimated molt status, as number of actively growing feathers. I found circulating plasma protein concentration to be lower in the fall during molt than during winter or summer. I also found a significant relationship between circulating protein levels and capture site, as well as novel links to molt state and pox presence, with urban birds, those infected with pox, and those in more intense molt having higher protein levels. My results support the hypotheses that plasma protein concentration can be indicative of a bird’s body molt (which demands considerable protein for feather synthesis) and degree of habitat urbanization, although future work is needed to determine why protein levels were higher in virus-infected birds.