Variation in human limb joint articular morphology

Objectives

Synovial joints in human limbs strike a balance between mobility, stability, and articular fit, yet little is known about how these conflicting demands pattern intraspecific variation in articular shape. In this study, we use geometric morphometrics to establish the apportionment and magnitude of morphological variance of the articular surfaces of the human shoulder, elbow, hip, and knee. We hypothesize that variances will be comparable between articulating surfaces within a joint and will be larger in joints with smaller ranges of motion, given their plurality of functional demands.

Materials and Methods

Three-dimensional landmarks were taken on the articular surfaces of the glenohumeral, humeroulnar, acetabulofemoral, and tibiofemoral joints from CT scans of 200 skeletons from the University of Tennessee Donated Skeletal Collection (84 females, 116 males). Root mean-squared distances between articulations calculated from Procrustes shape coordinates were used to determine variance distributions.

Results

We found no difference in variances for each articular surface between the sexes or between left and right articular surfaces. A high range of motion is associated with greater morphological variance; however, this pattern is largely driven by the concave articular surfaces of each joint, which consistently exhibit statistically greater variance than their convex counterparts.

Discussion

The striking pattern of differential variance between articulating morphologies points to potential disparities in development between them. Consistently higher variance in concave surfaces may relate to chondral modeling theory for the formation of joints. Establishing intraspecific morphological variance patterns is a first step in understanding coordinated evolution among articular features.     

A hybrid behavioural rule of adaptation and drift explains the emergent architecture of antagonistic networks

Ecological processes that can realistically account for network architectures are central to our understanding of how species assemble and function in ecosystems. Consumer species are constantly selecting and adjusting which resource species are to be exploited in an antagonistic network. Here we incorporate a hybrid behavioural rule of adaptive interaction switching and random drift into a bipartite network model. Predictions are insensitive to the model parameters and the initial network structures, and agree extremely well with the observed levels of modularity, nestedness and node-degree distributions for 61 real networks. Evolutionary and community assemblage histories only indirectly affect network structure by defining the size and complexity of ecological networks, whereas adaptive interaction switching and random drift carve out the details of network architecture at the faster ecological time scale. The hybrid behavioural rule of both adaptation and drift could well be the key processes for structure emergence in real ecological networks.     

Binding and Functional Folding (BFF): A Physiological Framework for Studying Biomolecular Interactions and Allostery

EF-hand Ca²⁺-binding proteins (CBPs), such as S100 proteins (S100s) and calmodulin (CaM), are signaling proteins that undergo conformational changes upon increasing intracellular Ca²⁺. Upon binding Ca²⁺, S100 proteins and CaM interact with protein targets and induce important biological responses. The Ca²⁺-binding affinity of CaM and most S100s in the absence of target is weak (^CaK_D > 1 μM). However, upon effector protein binding, the Ca²⁺ affinity of these proteins increases via heterotropic allostery (^CaK_D < 1 μM). Because of the high number and micromolar concentrations of EF-hand CBPs in a cell, at any given time, allostery is required physiologically, allowing for (i) proper Ca²⁺ homeostasis and (ii) strict maintenance of Ca²⁺-signaling within a narrow dynamic range of free Ca²⁺ ion concentrations, [Ca²⁺]^free. In this review, mechanisms of allostery are coalesced into an empirical “binding and functional folding (BFF)” physiological framework. At the molecular level, folding (F), binding and folding (BF), and BFF events include all atoms in the biomolecular complex under study. The BFF framework is introduced with two straightforward BFF types for proteins (type 1, concerted; type 2, stepwise) and considers how homologous and nonhomologous amino acid residues of CBPs and their effector protein(s) evolved to provide allosteric tightening of Ca²⁺ and simultaneously determine how specific and relatively promiscuous CBP-target complexes form as both are needed for proper cellular function.     

Inference of Multisite Phosphorylation Rate Constants and Their Modulation by Pathogenic Mutations

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Reductive Biotransformation of Benzaldehyde Derivatives by Baker's Yeast in Non-Conventional Media: Effect of Substrate Hydrophobicity on the Biocatalytic Reaction

The reduction of six derivatives of benzaldehyde, α,α,α-trifluorotolualdehyde, nitrobenzaldehyde, anisaldehyde, fluorobenzaldehyde, tolualdehyde, chlorobenzaldehyde, each of which was substituted in the ortho-, meta- and para-positions, was investigated in whole cell yeast biotransformations conducted in non-conventional media. Correlation between hydrophobic (π) and electronic (σ) parameters of the substituent of the substrate and biocatalytic activity in organic solvent media (hexane containing 2% v/v water) was evaluated. While catalytic activity in general decreased as the substituent hydrophobicity (π) increased, the trend was more pronounced for ortho- substituents compared to meta- and para-. When the electronic parameters (σ) of the meta- and para- substituents were correlated with the catalytic activity, the opposite was observed, namely the catalytic activity increased as the electronic parameter of the substituent increased. This observation was similar for meta- and para- substituents.

Preliminary studies on the relationships between solvent and substrate polarity on the one hand and catalytic activity on the other are also presented and discussed.