Factors Associated with Revision Surgery after Internal Fixation of Hip Fractures

Background: Femoral neck fractures are associated with high rates of revision surgery after management with internal fixation. Using data from the Fixation using Alternative Implants for the Treatment of Hip fractures (FAITH) trial evaluating methods of internal fixation in patients with femoral neck fractures, we investigated associations between baseline and surgical factors and the need for revision surgery to promote healing, relieve pain, treat infection or improve function over 24 months postsurgery. Additionally, we investigated factors associated with (1) hardware removal and (2) implant exchange from cancellous screws (CS) or sliding hip screw (SHS) to total hip arthroplasty, hemiarthroplasty, or another internal fixation device. Methods: We identified 15 potential factors a priori that may be associated with revision surgery, 7 with hardware removal, and 14 with implant exchange. We used multivariable Cox proportional hazards analyses in our investigation. Results: Factors associated with increased risk of revision surgery included: female sex, [hazard ratio (HR) 1.79, 95% confidence interval (CI) 1.25-2.50; P = 0.001], higher body mass index (fo

Conditions for liposome adsorption and bilayer formation on BSA passivated solid supports

Planar solid supported lipid membranes that include an intervening bovine serum albumen (BSA) cushion can greatly reduce undesirable interactions between reconstituted membrane proteins and the underlying substrate. These hetero-self-assemblies reduce frictional coupling by shielding reconstituted membrane proteins from the strong surface charge of the underlying substrate, thereby preventing them from strongly sticking to the substrate themselves. The motivation for this work is to describe the conditions necessary for liposome adsorption and bilayer formation on these hetero-self-assemblies. Described here are experiments that show that the state of BSA is critically important to whether a lipid bilayer is formed or intact liposomes are adsorbed to the BSA passivated surface. It is shown that a smooth layer of native BSA will readily promote lipid bilayer formation while BSA that has been denatured either chemically or by heat will not. Atomic force microscopy (AFM) and fluorescence microscopy was used to characterize the surfaces of native, heat denatured, and chemically reduced BSA. The mobility of several zwitterionic and negatively charged lipid combinations has been measured using fluorescence recovery after photobleaching (FRAP). From these measurements diffusion constants and percent recoveries have been determined and tabulated. The effect of high concentrations of beta-mercaptoethanol (β-ME) on liposome formation as well as bilayer formation was also explored

Single-Protein Tracking Reveals That NADPH Mediates the Insertion of Cytochrome P450 Reductase into a Biomimetic of the Endoplasmic Reticulum

Cytochrome P450 reductase (CPR) is the redox partner for most human cytochrome P450 enzymes. It is also believed that CPR is an integral membrane protein exclusively. Herein, we report that, contrary to this belief, CPR can exist as a peripheral membrane protein in the absence of NADPH and will transition to an integral membrane protein in the presence of stoichiometric amounts of NADPH or greater. All experiments were performed in a solid-supported cushioned lipid bilayer that closely matched the chemical composition of the human endoplasmic reticulum and served as an ER biomimetic. The phase characteristics and fluidity of the ER biomimetic was characterized with fluorescence micrographs and temperature-dependent fluorescence recovery after photobleaching. The interactions of CPR with the ER biomimetic were directly observed by tracking single CPR molecules using time-lapse single-molecule fluorescence imaging and subsequent analysis of tracks. These studies revealed dramatic changes in diffusion coefficient and the degree of partitioning of CPR as a function of NADPH concentration

Substrate Dependent Native Luminescence from Cytochromes P450 3A4, 2C9, and P450cam

Metalloporphyrin containing proteins, such as cytochrome P450, play a key role in biological systems. The spectroscopic properties of metalloporphyrins have been a subject of intense interest and intense debate for over 50 years. Iron-porphyrins are usually believed to be nonfluorescent. Herein we report that, contrary to this belief, cytochrome P450 heme groups luminesce with enough intensity to be of use in the characterization of these enzymes. To confirm that the emission is from the heme, we destroyed the heme by titration with cumene hydroperoxide and measured the changes in emission upon titration with compounds known to bind to the distal face of the heme in two human cytochrome P450 enzymes, known as CYP3A4 and CYP2C9. The titration curves gave spectral dissociation constants that were not significantly different from those reported using the Soret UV/vis absorbance changes. We have tentatively assigned the broad luminescence at ∼500 nm to a (1)ππ* → gs fluorescence and the structured luminescence above 600 nm to a (3)ππ* → gs phosphorescence. These assignments are not associated with the Q-band, and are in violation of Kasha's rule. To illustrate the utility of the emission, we measured spectral dissociation constants for testosterone binding to P450 3A4 in bilayers formed on glass coverslips, a measurement that would be very difficult to make using absorption spectroscopy. Complementary experiments were carried out with water-soluble P450cam

Tracking individual membrane proteins and their biochemistry: The power of direct observation

The advent of single molecule fluorescence microscopy has allowed experimental molecular biophysics and biochemistry to transcend traditional ensemble measurements, where the behavior of individual proteins could not be precisely sampled. The recent explosion in popularity of new super-resolution and super-localization techniques coupled with technical advances in optical designs and fast highly sensitive cameras with single photon sensitivity and millisecond time resolution have made it possible to track key motions, reactions, and interactions of individual proteins with high temporal resolution and spatial resolution well beyond the diffraction limit. Within the purview of membrane proteins and ligand gated ion channels (LGICs), these outstanding advances in single molecule microscopy allow for the direct observation of discrete biochemical states and their fluctuation dynamics. Such observations are fundamentally important for understanding molecular-level mechanisms governing these systems. Examples reviewed here include the effects of allostery on the stoichiometry of ligand binding in the presence of fluorescent ligands; the observation of subdomain partitioning of membrane proteins due to microenvironment effects; and the use of single particle tracking experiments to elucidate characteristics of membrane protein diffusion and the direct measurement of thermodynamic properties, which govern the free energy landscape of protein dimerization. The review of such characteristic topics represents a snapshot of efforts to push the boundaries of fluorescence microscopy of membrane proteins to the absolute limit. This article is part of the Special Issue entitled ‘Fluorescent Tools in Neuropharmacology’. •Mini-review with special emphasis on the power of direct observation.•Stochastic fluctuations can be used to build discrete state kinetic models.•Single protein tracking gives a realistic understanding of mass transport.•Identification of individual states can be used to determine chemical potential.•Super-resolution imaging can yield key information about compartmentalization

The taxonomic impediment: a shortage of taxonomists, not the lack of technical approaches.

Engel, Michael S, Ceríaco, Luis M P, Daniel, Gimo M, Dellapé, Pablo M, Löbl, Ivan, Marinov, Milen, Reis, Roberto E, Young, Mark T, Dubois, Alain, Agarwal, Ishan, Lehmann A., Pablo, Alvarado, Mabel, Alvarez, Nadir, Andreone, Franco, Araujo-Vieira, Katyuscia, Ascher, John S, Baêta, Délio, Baldo, Diego, Bandeira, Suzana A, Barden, Phillip, Barrasso, Diego A, Bendifallah, Leila, Bockmann, Flávio A, Böhme, Wolfgang, Borkent, Art, Brandão, Carlos R F, Busack, Stephen D, Bybee, Seth M, Channing, Alan, Chatzimanolis, Stylianos, Christenhusz, Maarten J M, Crisci, Jorge V, D'elía, Guillermo, Da Costa, Luis M, Davis, Steven R, De Lucena, Carlos Alberto S, Deuve, Thierry, Fernandes Elizalde, Sara, Faivovich, Julián, Farooq, Harith, Ferguson, Adam W, Gippoliti, Spartaco, Gonçalves, Francisco M P, Gonzalez, Victor H, Greenbaum, Eli, Hinojosa-Díaz, Ismael A, Ineich, Ivan, Jiang, Jianping, Kahono, Sih, Kury, Adriano B, Lucinda, Paulo H F, Lynch, John D, Malécot, Valéry, Marques, Mariana P, Marris, John W M, Mckellar, Ryan C, Mendes, Luis F, Nihei, Silvio S, Nishikawa, Kanto, Ohler, Annemarie, Orrico, Victor G D, Ota, Hidetoshi, Paiva, Jorge, Parrinha, Diogo, Pauwels, Olivier S G, Pereyra, Martín O, Pestana, Lueji B, Pinheiro, Paulo D P, Prendini, Lorenzo, Prokop, Jakub, Rasmussen, Claus, Rödel, Mark-Oliver, Rodrigues, Miguel Trefaut, Rodríguez, Sara M, Salatnaya, Hearty, Sampaio, Íris, Sánchez-García, Alba, Shebl, Mohamed A, Santos, Bruna S, Solórzano-Kraemer, Mónica M, Sousa, Ana C A, Stoev, Pavel, Teta, Pablo, Trape, Jean-François, Dos Santos, Carmen Van-Dúnem, Vasudevan, Karthikeyan, Vink, Cor J, Vogel, Gernot, Wagner, Philipp, Wappler, Torsten, Ware, Jessica L, Wedmann, Sonja, Zacharie, Chifundera Kusamba (2021): EDITORIAL The taxonomic impediment: a shortage of taxonomists, not the lack of technical approaches. Zoological Journal of the Linnean Society 193 (2): 381-387, DOI: 10.1093/zoolinnean/zlab072, URL: https://academic.oup.com/zoolinnean/article/193/2/381/637438