Protein dynamics govern the oxyferrous state lifetime of an artificial oxygen transport protein.

It has long been known that the alteration of protein side chains that occlude or expose the heme cofactor to water can greatly affect the stability of the oxyferrous heme state. Here, we demonstrate that the rate of dynamically driven water penetration into the core of an artificial oxygen transport protein also correlates with oxyferrous state lifetime by reducing global dynamics, without altering the structure of the active site, via the simple linking of the two monomers in a homodimeric artificial oxygen transport protein using a glycine-rich loop. The tethering of these two helices does not significantly affect the active site structure, pentacoordinate heme-binding affinity, reduction potential, or gaseous ligand affinity.

Developing the Ce and La pair as companion positron emission tomography diagnostic isotopes for Ac and Th radiotherapeutics.

Developing targeted α-therapies has the potential to transform how diseases are treated. In these interventions, targeting vectors are labelled with α-emitting radioisotopes that deliver destructive radiation discretely to diseased cells while simultaneously sparing the surrounding healthy tissue. Widespread implementation requires advances in non-invasive imaging technologies that rapidly assay therapeutics.

Unwinding of the Substrate Transmembrane Helix in Intramembrane Proteolysis.

Intramembrane-cleaving proteases (I-CLiPs) activate pools of single-pass helical membrane protein signaling precursors that are key in the physiology of prokaryotic and eukaryotic cells. Proteases typically cleave peptide bonds within extended or flexible regions of their substrates, and thus the mechanism underlying the ability of I-CLiPs to hydrolyze the presumably α-helical transmembrane domain (TMD) of these membrane proteins is unclear. Using deep-ultraviolet resonance Raman spectroscopy in combination with isotopic labeling, we show that although predominantly in canonical α-helical conformation, the TMD of the established I-CLiP substrate Gurken displays 3-helical geometry.

Site-directed mutagenesis of the highly perturbed copper site of auracyanin D.

Type-1 copper proteins participate in redox reactions and biological catalysis. Significant variation exists within the electronic structure of type-1 copper sites, producing both blue and green proteins. Classical, "blue" sites have been extensively studied, but "green" sites have been poorly characterized.

Effects of fluidity on the ensemble structure of a membrane embedded α-helical peptide.

Melittin, the main hemolytic component of honeybee venom, is unfolded in an aqueous environment and folds into an α-helical conformation in a lipid environment. Membrane fluidity is known to affect the activity and structure of melittin. By combining two structurally sensitive optical methods, circular dichroism (CD) and deep-ultraviolet resonance Raman spectroscopy (dUVRR), we have identified distinct structural fluctuations in melittin correlated with increased and decreased 1,2-dimyristoyl-sn-glycero-3-phosphocholine bilayer fluidities.

Role of bilayer characteristics on the structural fate of aβ(1-40) and aβ(25-40).

The β-amyloid (Aβ) peptide is derived from the transmembrane (TM) helix of the amyloid precursor protein (APP) and has been shown to interact with membrane surfaces. To understand better the role of peptide-membrane interactions in cell death and ultimately in Alzheimer's disease, a better understanding of how membrane characteristics affect the binding, solvation, and secondary structure of Aβ is needed. Employing a combination of circular dichroism and deep-UV resonance Raman spectroscopies, Aβ(25-40) was found to fold spontaneously upon association with anionic lipid bilayers.

Bilayer surface association of the pHLIP peptide promotes extensive backbone desolvation and helically-constrained structures.

Despite their presence in many aspects of biology, the study of membrane proteins lags behind that of their soluble counterparts. Improving structural analysis of membrane proteins is essential. Deep-UV resonance Raman (DUVRR) spectroscopy is an emerging technique in this area and has demonstrated sensitivity to subtle structural transitions and changes in protein environment.

Metalloproteins diversified: the auracyanins are a family of cupredoxins that stretch the spectral and redox limits of blue copper proteins.

The metal sites of electron transfer proteins are tuned for function. The type 1 copper site is one of the most utilized metal sites in electron transfer reactions. This site can be tuned by the protein environment from +80 mV to +680 mV in typical type 1 sites.

Protein conformational changes involved in the cytochrome bc1 complex catalytic cycle.

Early structures of the cytochrome bc1 complex revealed heterogeneity in the position of the soluble portion of the Rieske iron sulfur protein subunit, implicating a movement of this domain during function. Subsequent biochemical and biophysical works have firmly established that the motion of this subunit acts in the capacity of a conformationally assisted electron transfer step during the already complicated catalytic mechanism described within the modified version of Peter Mitchells Q cycle. How the movement of this subunit is initiated or how the frequency of its motion is controlled as a function of other steps during the catalysis remain topics of debate within the active research communities.

Observation of persistent α-helical content and discrete types of backbone disorder during a molten globule to ordered peptide transition via deep-UV resonance Raman spectroscopy.

The molten globule state can aide in the folding of a protein to a functional structure and is loosely defined as an increase in structural disorder with conservation of the ensemble secondary structure content. Simultaneous observation of persistent secondary structure content with increased disorder has remained experimentally problematic. As a consequence, modeling how the molten globule state remains stable and how it facilitates proper folding remains difficult due to a lack of amenable spectroscopic techniques to characterize this class of partially unfolded proteins.

Proton radiography peers into metal solidification.

Historically, metals are cut up and polished to see the structure and to infer how processing influences the evolution. We can now peer into a metal during processing without destroying it using proton radiography. Understanding the link between processing and structure is important because structure profoundly affects the properties of engineering materials.

An invitation to the 16th international congress on photosynthesis research in 2013: opportunities and challenges in the 21st century.

The 16th International Congress on Photosynthesis will be held August 11-16, 2013 in St. Louis, Missouri, USA. The congress will include 15 plenary lectures, 21 scientific symposia, poster sessions, exhibitors, opening reception, final banquet, excursions and accompanying persons program.

Long range order and two-fluid behavior in heavy electron materials.

The heavy electron Kondo liquid is an emergent state of condensed matter that displays universal behavior independent of material details. Properties of the heavy electron liquid are best probed by NMR Knight shift measurements, which provide a direct measure of the behavior of the heavy electron liquid that emerges below the Kondo lattice coherence temperature as the lattice of local moments hybridizes with the background conduction electrons. Because the transfer of spectral weight between the localized and itinerant electronic degrees of freedom is gradual, the Kondo liquid typically coexists with the local moment component until the material orders at low temperatures.

Influence of the lipid environment on valinomycin structure and cation complex formation.

Carrier-type molecular ionophores, such as the cyclic dodecadepsipeptide valinomycin, often must undergo structural changes during the binding and transport of a cation across the lipid membrane. Observing the structural fluctuations that occur during this process experimentally has proven extremely difficult due to the complexities of spectroscopic analysis of protein structure/dynamics in native lipid bilayer environments. Currently, our understanding of how valinomycin selectively transports ions across membranes is derived from atomic structures solved of the cyclic macromolecule solvated in various organic solvents and complimentary in silico dynamics experiments.

Deep-UV resonance Raman analysis of the Rhodobacter capsulatus cytochrome bc₁complex reveals a potential marker for the transmembrane peptide backbone.

Classical strategies for structure analysis of proteins interacting with a lipid phase typically correlate ensemble secondary structure content measurements with changes in the spectroscopic responses of localized aromatic residues or reporter molecules to map regional solvent environments. Deep-UV resonance Raman (DUVRR) spectroscopy probes the vibrational modes of the peptide backbone itself, is very sensitive to the ensemble secondary structures of a protein, and has been shown to be sensitive to the extent of solvent interaction with the peptide backbone [ Wang , Y. , Purrello , R.

Loss of a conserved tyrosine residue of cytochrome b induces reactive oxygen species production by cytochrome bc1.

Production of reactive oxygen species (ROS) induces oxidative damages, decreases cellular energy conversion efficiencies, and induces metabolic diseases in humans. During respiration, cytochrome bc(1) efficiently oxidizes hydroquinone to quinone, but how it performs this reaction without any leak of electrons to O(2) to yield ROS is not understood. Using the bacterial enzyme, here we show that a conserved Tyr residue of the cytochrome b subunit of cytochrome bc(1) is critical for this process.

A structural model for across membrane coupling between the Qo and Qi active sites of cytochrome bc1.

The two spatially distant quinone-binding sites of the ubihydroquinone: cytochrome c oxidoreductase (cyt bc(1)) complex have been shown to influence one another in some fashion. This transmembrane communication alters cofactor and redox partner binding interactions and could potentially influence the timing or 'concerted' steps involved in the steady-state turnover of the homodimeric enzymes. Yet, despite several lines of evidence corroborating the coupling of the quinone binding active sites to one another, little to no testable hypothesis has been offered to explain how such a "signal" might be transmitted across the presumably rigid hydrophobic domain of the enzyme.

Across membrane communication between the Q(o) and Q(i) active sites of cytochrome bc(1).

The ubihydroquinone:cytochrome c oxidoreductase (cyt bc(1)) contains two catalytically active domains, termed the hydroquinone oxidation (Q(o)) and quinone reduction (Q(i)) sites, which are distant from each other by over 30 A. Previously, we have reported that binding of inhibitors to the Q(i) site on one (n) side of the energy-transducing membrane changes the local environment of the iron-sulfur (Fe/S) protein subunit residing in the Q(o) site on the other (p) side of the lipid bilayer [Cooley, J. W.

Cytochrome bc1-cy fusion complexes reveal the distance constraints for functional electron transfer between photosynthesis components.

Photosynthetic (Ps) growth of purple non-sulfur bacteria such as Rhodobacter capsulatus depends on the cyclic electron transfer (ET) between the ubihydroquinone (QH2): cytochrome (cyt) c oxidoreductases (cyt bc1 complex), and the photochemical reaction centers (RC), mediated by either a membrane-bound (cyt c(y)) or a freely diffusible (cyt c2) electron carrier. Previously, we constructed a functional cyt bc1-c(y) fusion complex that supported Ps growth solely relying on membrane-confined ET ( Lee, D.-W.

Site-specific fracture plane determination using the FIB/TEM.

A new method for the determination of the crystallographic indices of planar fracture surfaces is described. The key innovation is the use of a focused ion beam instrument to extract two transmission electron microscopy (TEM) foils from the fracture surface. Selected area diffraction of these foils in the TEM allows the determination of the fracture plane from the cross product of two crystallographic line directions contained within the plane.

A functional hybrid between the cytochrome bc1 complex and its physiological membrane-anchored electron acceptor cytochrome cy in Rhodobacter capsulatus.

The membrane integral ubihydroquinone (QH2): cytochrome (cyt) c oxidoreductase (or the cyt bc1 complex) and its physiological electron acceptor, the membrane-anchored cytochrome cy (cyt cy), are discrete components of photosynthetic and respiratory electron transport chains of purple non-sulfur, facultative phototrophic bacteria of Rhodobacter species. In Rhodobacter capsulatus, it has been observed previously that, depending on the growth condition, absence of the cyt bc1 complex is often correlated with a similar lack of cyt cy (Jenney, F. E.

Use of gyroscopic sensors for objective evaluation of trimming and shoeing to alter time between heel and toe lift-off at end of the stance phase in horses walking and trotting on a treadmill.

Objective: To determine whether a shoe with an axialcontoured lateral branch would induce greater lateral roll of the forelimb hoof during the time between heel and toe lift-off at end of the stance phase (breakover). Animals-10 adult horses.

Procedure: A gyroscopic transducer was placed on the hoof of the right forelimb and connected to a transmitter.