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Abstract Eggshells are daily food waste disposed of in landfills, producing environmental issues and an unpleasant odour. Eggshells powder may be suitably applied as a filler in epoxy resins to improve their mechanical properties. The material properties and fracture energy of toughened epoxy with eggshell powder (TEEP) were measured and investigated. Dog-bone specimens were fabricated to investigate the mechanical properties of TEEP (i.e. elastic modulus, Poisson’s ratios and tensile strength) and tested under quasi-static tensile loading. Double Cantilever Beam (DCB) and End-Notched Flexure (ENF) tests were used to determine the mode I and Mode II fracture energies of TEEP specimens, respectively. For this purpose, oven-dried eggshells were crushed into particles size of 100 µm. The volume fraction of eggshell powder as filler in TEEP is designated as 0%, 2.5%, 5%, and 10%. The epoxy resin system was made by mixing EPIKOTE Resin 828 and Hardener 651 with a mixing ratio of 5:2 by weight. The results showed that the tensile strength, elastic modulus, fracture energy in Mode I and Mode II were optimum at TEEP 5% with an enhancement of 36.8%, 24.9%, 60.3% and 166.3%, respectively compared to that of neat epoxy. This is due to better surface roughness and the ability of eggshell powder as a crack arrestor. However, TEEP with 10% eggshell prone to agglomeration of eggshell powder caused poor bonding with epoxy resin and affect the mechanical properties. [ABSTRACT FROM AUTHOR]

An experimental study to investigate the load at failure, failure mechanism, and crack propagation of a notched foamed concrete beam externally reinforced with a 200 mm length kenaf fiber reinforced polymer (KFRP) and tested under a four-point bending test (4PBT) is presented. In this study, the notch depth was varied. KFRP plates were fabricated by placing weaved yarns and smeared with Sika S31. From the experimental work, the shear failure and FRP rupture were seen. Various normalized notch depths significantly influenced allowable ultimate displacement, crack initiation, and failure modes. Following the preceding experimental series, a 2-D numerical modeling framework was developed to simulate the failure of the KFRP-strengthened foamed concrete beam. Independent tests had been carried out to determine material properties of the foamed concrete beam (i.e., un-notched beam strength, σ o and fracture energy, G c ), later they were incorporated within a traction–separation relationship as a constitutive model of finite element modeling. The fracture energy values were calculated using Hillerborg's model, which agrees well with the previous literature. Extended finite element model techniques were adopted for the strength prediction works. A good agreement was found between the predicted and experimental results with discrepancies of less than 15%. [ABSTRACT FROM AUTHOR]

This paper investigates the effect of KFRP composite sheets as a strengthening material in improving the load-carrying resistance of lightweight foam concrete beams using a FEA modelling framework. The study employed three parametric strengthening schemes (i.e., KFRP length, woven architecture types and KFRP thickness). Twenty-seven beam specimens were tested, and respective failure modes and ultimate load at failure were discussed. All the strengthened beam specimens failed mostly in shear mode and, to a lesser extent, in FRP fracture. Despite the absence of de-bonding failure, improvement of strengthening using KFRP sheet technique was exhibited. Later, Extended Finite Element Method (XFEM) Modelling was incorporated following failure mode exhibited. Strength predictions incorporating the traction-separation relationship using XFEM techniques. Validation work with experimental datasets showed good agreements with average discrepancies of less than 10%. The numerical approach can be used as a strength prediction tool in concrete beams with externally bonded FRPs. [ABSTRACT FROM AUTHOR]

Diphtheria toxin (DT) is the archetype for bacterial exotoxins implicated in human diseases and has played a central role in defining the field of toxinology since its discovery in 1888. Despite being one of the most extensively characterized bacterial toxins, the origins and evolutionary adaptation of DT to human hosts remain unknown. Here, we determined the first high-resolution structures of DT homologs outside of the Corynebacterium genus. DT homologs from Streptomyces albireticuli (17% identity to DT) and Seinonella peptonophila (20% identity to DT), despite showing no toxicity toward human cells, display significant structural similarities to DT sharing both the overall Y-shaped architecture of DT as well as the individual folds of each domain. Through a systematic investigation of individual domains, we show that the functional determinants of host range extend beyond an inability to bind cellular receptors; major differences in pH-induced pore-formation and cytosolic release further dictate the delivery of toxic catalytic moieties into cells, thus providing multiple mechanisms for a conserved structural fold to adapt to different hosts. Our work provides structural insights into the expanding DT family of toxins, and highlights key transitions required for host adaptation. Toxic proteins are responsible for the disease symptoms accompanying bacterial infections. Sugiman-Marangos et al. report crystal structures of two diphtheria toxin homologs, therefore providing structural insights into this family of toxins and the evolutionary adaptation of these toxins to human hosts. [ABSTRACT FROM AUTHOR]

The aim of the current project is to carry out the FEA framework for predicting the flexural strength of notched foam concrete tested under three-point bending following the conducted experimental set-up. The investigated testing series have a variation of notch size opening in the foamed concrete beam. The Tractionseparation relationship was used as a constitutive model to incorporate independent material properties and used in the modelling framework. Modelling techniques of 2D XFEM and CZM were adopted and later expanded to 3D XFEM models. Good agreement was found between the predicted structure response and experimental observation for all the investigated models. Crack was initiated at the crack tip and propagated to the beam edge under the applied load. It was found that the average discrepancies below 20% were found within XFEM techniques. Less agreement was found using the CZM models, partly due to the simplification of the adopted failure path. The modelling framework implemented in this project is potentially used as a predictive tool in estimating the flexural strength of the concrete beam with notches. [ABSTRACT FROM AUTHOR]

The study investigated the effects of ageing on the tensile properties and fracture behaviour of an epoxy filled with inorganic fillers having different reactivity to water, such as fly ash, calcium carbonate (CaCO3), and Portland cement. CaCO3 is insoluble in water, whereas fly ash and cement are reactive to water; however, fly ash is less reactive than cement. The water absorption, tensile properties, and mode-I fracture toughness of the epoxy containing 7 wt% of filler were compared after ageing the composites in distilled water at 50 °C. Gravimetric analyses showed that compared to neat epoxy, CaCO3 slightly decreased the equilibrium water uptake of the filled epoxy, whereas fly ash and cement increased the equilibrium water uptake. Compared to the other fillers, the tensile strength of CaCO3-filled epoxy was inferior in both dry and wet conditions. However, in dry condition, the elastic modulus of CaCO3-filled epoxy was slightly higher. Overall, the fly ash-filled epoxy showed better tensile and fracture properties in both dry and wet conditions although it absorbed more water than the other fillers did. Scanning electron microscopy revealed that crack deflection played a dominant role in the toughening of filled epoxies in both dry and wet conditions. [ABSTRACT FROM AUTHOR]

This paper presents the water uptake and its effect on the tensile properties and the translaminar fracture toughness of glass fiber reinforced unsaturated polyester composites (GFRUPs) aged in distilled and saltwater at a temperature of 50 °C, in steady and fluctuating conditions. In both conditions, the GFRUPs aged in distilled water absorbed more water than in saltwater. The tensile strength of GFRUP tends to decrease with the immersion time in both aging media, but the decrease of tensile strength in saltwater is worse than that in distilled water. In steady condition, the translaminar fracture toughness increases after 7 days immersion and then tends to decrease beyond that immersion time. While in fluctuating condition, the translaminar fracture toughness increases until 15 days immersion and then gradually decreases up to 30 days immersion. Overall, the degradation of mechanical properties in the fluctuating condition is lower than in the steady condition. [ABSTRACT FROM AUTHOR]

The article presents a study which adopted the strategy by diphtheria toxin to enter into the endolysosomal network of cells by creating a chimera between the receptor-binding fragment of diphtheria toxin and lysosomal hydrolase tripeptidyl peptidase-1 (TPP1) to improve the effectiveness of enzyme replacement therapy as treatment of lysosomal storage diseases (LSD). Based on the results, chimeric TPP1 binds strongly to target cells.

The current paper aimed to model failures and fractures in single-lap bolted joints of woven fabric kenaf fiber reinforced polymer (KFRP) composite plate to fail in net-tension. The approach was based on the assumptions that micro-damage events were densely concentrated ahead of the notch tip and crack growth were readily seen along net-tension plane in a self-similar fashion. A 3-D finite element modelling framework were developed to explicitly incorporate bolt clamp-up in a range of KFRP series following tested experimental datasets. Lay-up types, normalized W/d, temperature exposure with constant bolt torque of 5 Nm were considered. It was found that KFRP plates under elevated temperature were stronger than under room temperature due to matrix toughening. Traction-separation relationship was incorported within Extended Finite Element Method (XFEM) framework to model damage within KFRP composite plate by using independent experimental datasets, here incorporates un-notched plate strength, so and fracture toughness, Gc of all testing lay-ups. Constitutive model used is associated with stress concentration, therefore good agreement between predicted and experimental bearing stress at failure with net-tension failure mode is perhaps not suprising. [ABSTRACT FROM AUTHOR]

The paper presents a comparison of the cohesive zone model (CZM) and the continuum damage mechanics approach in predicting the static failure of a single lap joint (SLJ). The effect of mesh size and viscosity were studied to give more understanding on the failure load and computational time. Both the load–displacement response and the backface strain technique were utilised to compare the validity of predictions. Peel and shear stress and damage distributions along with the damage progression are compared to understand the behaviour of the models in predicting the static failure response. In general, both approaches show good accuracy in predicting the failure load; however, the cohesive zone approach requires shorter computation time than the continuum damage approach. The continuum damage approach shows some mesh-dependency particularly for elements with high aspect ratios, whereas the cohesive zone approach is not. The continuum damage approach is less sensitive than the cohesive zone approach to the artificial damping required to achieve convergence. Another interesting finding is using the same ultimate stress level of damage in the continuum damage approach at the peak load is much lower than that in the cohesive approach; but the failure process in this approach is faster. [ABSTRACT FROM PUBLISHER]

This paper presents the water diffusion behaviour, tensile properties and fracture toughness of epoxy after it is aged in distilled and salt water in both steady and fluctuating conditions at a temperature of 50 °C. In steady and fluctuating conditions, the equilibrium water uptake of epoxy aged in salt water is lower than that in distilled water, but the diffusion rate is unaffected. The effects of the media and ageing condition on the tensile properties and fracture toughness are insignificant. The absorbed water (0.6–1.8%) improves the epoxy fracture toughness up to three times, which is indicated by the complex fracture surfaces of aged epoxy. [ABSTRACT FROM AUTHOR]

Diphtheria toxin (DT), produced by Corynebacterium diphtheria, is the causative agent of diphtheria and one of the most potent protein toxins known; however, it has an unclear evolutionary history. Here, we report the discovery of a DT‐like gene family in several bacterial lineages outside of Corynebacterium, including Austwickia and Streptomyces. These DT‐like genes form sister lineages in the DT phylogeny and conserve key DT features including catalytic and translocation motifs, but possess divergent receptor‐binding domains. DT‐like genes are not associated with corynephage, but have undergone lateral transfer through a separate mechanism. The discovery of the first non‐Corynebacterium homologs of DT sheds light on its evolutionary origin and highlights novelties that may have resulted in the emergence of DT targeting humans. [ABSTRACT FROM AUTHOR]

Experimental studies have been undertaken to investigate the static and fatigue responses of metal laminate doublers (MLD) joints under tension loading after ageing in deionised water at a temperature of 50 °C up to 2 years. It was found that absorbed water did not have a significant effect on the static and fatigue degradation of the MLD; however, corrosion pits located on the aluminium surfaces caused a reduction in fatigue life. Inevitably, the laminate contained butts where co-planar aluminium sheets were joined, and it was found that the position of the butt affected the static response of the MLD but, due to a restricted data set, it has not been possible to assess the effect under fatigue loading. The backface strain technique in conjunction with video microscopy has been utilised to monitor the damage of the adhesive bondlines, the butts and the aluminium layers and successfully identified both the localised and the global damage in the MLD. Most of fatigue failures initiated at the stringer bondline edge and at the aluminium layers where the butt was located. A careful design should be made to reduce the stress concentration at the stringer edge and to avoid positioning the butts at the upper layer of aluminium close to the stringer edge. [ABSTRACT FROM PUBLISHER]

Despite enormous efforts, achieving efficacious levels of proteins inside mammalian cells remains one of the greatest challenges in biologics-based drug discovery and development. The inability of proteins to readily cross biological membranes precludes access to the wealth of intracellular targets and applications that lie within mammalian cells. Existing methods of delivery commonly suffer from an inability to target specific cells and tissues, poor endosomal escape, and limited in vivo efficacy. The aim of the present commentary is to highlight the potential of certain classes of bacterial toxins, which naturally deliver a large protein into the cytosolic compartment of target cells after binding a host cell-surface receptor with high affinity, as robust protein delivery platforms. We review the progress made in recent years toward demonstrating the utility of these systems at delivering a wide variety of protein cargo, with special attention paid to three distinct toxin-based platforms. We contend that with recent advances in protein deimmunization strategies, bacterial toxins are poised to introduce biologics into the inner sanctum of cells and treat a wealth of heretofore untreatable diseases with a new generation of therapeutics. [ABSTRACT FROM AUTHOR]

Abstract: Experimental and numerical studies have been undertaken on hybrid fibre–metal (aluminium–Glare) laminate (FML) doubler joints to investigate their static response under tension loading. The specimens either have the fibres parallel to the loading direction (spanwise) or perpendicular to the loading direction (chordwise). Inevitably sheets in these laminates butt together and these butts can affect the joint strength. The effect of the butt position was investigated. The spanwise specimen was found to have the highest strength followed by chordwise specimens without butts and finally chordwise specimens with butts. The most critical position for a butt was found to be adjacent to the doubler end. The ultimate strength for spanwise and chordwise specimens without butts was controlled by the failure in the Glare layer, however, for specimens with butts, the butts control the ultimate strength. A progressive damage numerical analysis was undertaken using cohesive zone elements to model failure in the Glare and in the adhesive layers. This modelling was found to be in good agreement with the experiment data both in terms of the strength and the failure mechanisms. [Copyright &y& Elsevier]

• The combined effect of hydrophobic nano calcium carbonate content and temperature on water absorption of epoxy nanocomposites was investigated. • Anomalous water absorption in the hydrophobic nano calcium carbonate/epoxy nanocomposites was observed. • Hydrophobic nano calcium carbonate increased water absorption of epoxy nanocomposites. • The tensile properties of hydrophobic nano calcium carbonate/epoxy nanocomposites were improved both in unaged and aged condition. In this study, we investigated the effects of the filler content and ageing temperature on the water absorption and tensile properties of hydrophobic nano-calcium carbonate (NCC)/epoxy nanocomposites. The NCC content of the nanocomposites was varied from 0 to 5 wt%, while the ageing temperature was set at 28, 45, and 55°C in a distilled water bath. The nanocomposites exhibited the non-Fickian behaviour at all the NCC contents and ageing temperatures. In general, the water absorption of the nanocomposites increased after the addition of NCC. Meanwhile, the diffusivity of the nanocomposites decreased with an increase in the NCC content; however, this decrease became less significant at higher ageing temperatures. Although the addition of 1–3 wt% NCC significantly increased the water uptake capability of the nanocomposites, it resulted in an improvement in their tensile properties at high temperatures and prolonged ageing times. [ABSTRACT FROM AUTHOR]

Accurate pairing of DNA strands is essential for repair of DNA double-strand breaks (DSBs). How cells achieve accurate annealing when large regions of single-strand DNA are unpaired has remained unclear despite many efforts focused on understanding proteins, which mediate this process. Here we report the crystal structure of a single-strand annealing protein [DdrB (DNA damage response B)] in complex with a partially annealed DNA intermediate to 2.2 Å. This structure and supporting biochemical data reveal a mechanism for accurate annealing involving DdrB-mediated proofreading of strand complementarity. DdrB promotes high-fidelity annealing by constraining specific bases from unauthorized association and only releases annealed duplex when bound strands are fully complementary. To our knowledge, this mechanism provides the first understanding for how cells achieve accurate, protein-assisted strand annealing under biological conditions that would otherwise favor misannealing. [ABSTRACT FROM AUTHOR]

Type IV pili (T4P) contain hundreds of major subunits, but minor subunits are also required for assembly and function. Here we show that Pseudomonas aeruginosa minor pilins prime pilus assembly and traffic the pilus-associated adhesin and anti-retraction protein, PilY1, to the cell surface. PilV, PilW, and PilX require PilY1 for inclusion in surface pili and vice versa, suggestive of complex formation. PilE requires PilVWXY1 for inclusion, suggesting that it binds a novel interface created by two or more components. FimU is incorporated independently of the others and is proposed to couple the putative minor pilin-PilY1 complex to the major subunit. The production of small amounts of T4P by a mutant lacking the minor pilin operon was traced to expression of minor pseudopilins from the P. aeruginosa type II secretion (T2S) system, showing that under retraction-deficient conditions,T2Sminor subunits can prime T4P assembly. Deletion of all minor subunits abrogated pilus assembly. In a strain lacking the minor pseudopilins, PilVWXY1 and either FimU or PilE comprised the minimal set of components required for pilus assembly. Supporting functional conservation of T2S and T4P minor components, our 1.4 Å crystal structure of FimU revealed striking architectural similarity to its T2S ortholog GspH, despite minimal sequence identity. We propose that PilVWXY1 form a priming complex for assembly and that PilE and FimU together stably couple the complex to the major subunit. Trafficking of the anti-retraction factor PilY1 to the cell surface allows for production of pili of sufficient length to support adherence and motility. [ABSTRACT FROM AUTHOR]

Numerical literacy refers to the knowledge and ability to use various numbers and basic mathematical symbols to solve problems, while math self-concept means the assessment of students' skills, abilities, enjoyment, and interest in the subject. However, children with special needs and normal students in inclusive Elementary Schools are yet to sufficiently acquire learning that accommodates literacy and maths self-concept. This causes a need for the implementation of a children-friendly learning process. Therefore, this study aimed to identify the factors influencing the numeracy level and math self-concept, and also explore the obstacles in implementing children-friendly learning in order to facilitate students' abilities. A qualitative method was applied because of in-depth data exploration regarding children with special needs, while the utilized instruments include tests, questionnaires, and interviews. Both the data collected and the analysis are qualitative, which are obtained through excavation, identification, and description. Consequently, this paper was able to (a) describe the factors influencing the numeracy level and math self-concept in inclusive elementary schools; (b) explore the barriers to implementing children-friendly learning; and (c) identify the relationship between students' numeracy and math self-concept. [ABSTRACT FROM AUTHOR]

DNA-dependent protein kinase (DNA-PK) orchestrates DNA repair by regulating access to breaks through autophosphorylations within two clusters of sites (ABCDE and PQR). Blocking ABCDE phosphorylation (by alanine mutation) imparts a dominant negative effect, rendering cells hypersensitive to agents that cause DNA double-strand breaks. Here, a mutational approach is used to address the mechanistic basis of this dominant negative effect. Blocking ABCDE phosphorylation hypersensitizes cells to most types of DNA damage (base damage, cross-links, breaks, and damage induced by replication stress), suggesting that DNA-PK binds DNA ends that result from many DNA lesions and that blocking ABCDE phosphorylation sequesters these DNA ends from other repair pathways. This dominant negative effect requires DNA-PK's catalytic activity, as well as phosphorylation of multiple (non-ABCDE) DNA-PK catalytic subunit (DNA-PKcs) sites. PSIPRED analysis indicates that the ABCDE sites are located in the only contiguous extended region of this huge protein that is predicted to be disordered, suggesting a regulatory role(s) and perhaps explaining the large impact ABCDE phosphorylation has on the enzyme's function. Moreover, additional sites in this disordered region contribute to the ABCDE cluster. These data, coupled with recent structural data, suggest a model whereby early phosphorylations promote initiation of nonhomologous end joining (NHEJ), whereas ABCDE phosphorylations, potentially located in a "hinge" region between the two domains, lead to regulated conformational changes that initially promote NHEJ and eventually disengage NHEJ. [ABSTRACT FROM AUTHOR]

Summary: The study of biological transporters can be hampered by a dearth of methodology for tracking their activity within cells. Here, we present a means of monitoring the function of transport machinery within bacteria, exploiting a genetically encoded riboswitch-based sensor to detect the accumulation of the substrate in the cytoplasm. This method was used to investigate the model ABC transporter BtuC2D2F, which permits vitamin B12 uptake in Escherichia coli. We exploited the wealth of structural data available for this transporter to probe the functional and mechanistic importance of key residues of the substrate binding protein BtuF that are predicted to support its interaction with its substrate or with the BtuC channel-forming subunits. Our results reveal molecular interaction requirements for substrate binding proteins and demonstrate the utility of riboswitch-based sensors in the study of biological transport. [ABSTRACT FROM AUTHOR]

Abstract: Experimental studies have been undertaken investigating the effect of moisture on the fatigue response of adhesively bonded monolithic single lap joints and laminated doublers loaded in bending, both made of the same materials. The joints were aged in deionised water at a temperature of 50°C for up to 2 years exposure. The backface strain technique was employed to monitor damage initiation and propagation in the joints. The test results show that the fatigue life degraded with increasing moisture content and tended to level off when approaching saturation. The failure surfaces were cohesive in the adhesive. Numerical fatigue modelling has been undertaken to predict the fatigue response of these joints utilising a strain-based fatigue damage law integrated with a bilinear traction-separation cohesive zone model. The residual stresses due to thermal and swelling strain were included in the model. Good agreement was found between the predicted fatigue response and the experimental results. [Copyright &y& Elsevier]

Abstract: A cohesive zone model has been used to model the progressive damage in adhesively bonded aluminium monolithic single lap joints and laminated doublers. The backface strain technique was used to monitor the damage process in the adhesive layer and was also key in the calibration of a unique set of cohesive zone properties in the single lap joint. Further, this backface strain technique has been successfully used to assess the effect of substrate plasticity, position of cohesive elements, traction and fracture energy, and adhesive fillet in a monolithic single joint. The calibrated cohesive properties have then been successfully used to predict the static strength and backface strain response of the doublers in bending. [Copyright &y& Elsevier]

Abstract: The aim of this research is to investigate the effect of moisture on the static response of adhesively bonded monolithic single lap joints and laminated doublers loaded in bending. All joints were made of aluminium alloy Al 2024-T3 bonded using epoxy film adhesive FM 73M OST. The joints were aged in deionised water at a temperature of 50°C for up to 2 years exposure. The use of different widths of specimen (5mm for monolithic single lap joints and 15mm for laminated doublers) allowed both full and partial saturation of the adhesive layer. The bulk adhesive has been characterised to obtain the coefficient of moisture diffusion, the coefficient of thermal and moisture expansion and the moisture dependent mechanical properties. The testing results showed that the mechanical properties degraded in a linear way with the moisture content. The residual strength after exposure decreased with increasing moisture content (exposure time) and tended to level off towards saturation. The damage evolution and failure of the joint has been successfully monitored using the backface strain technique and in-situ video microscopy. Progressive damage finite element modelling using a moisture dependent, bilinear traction-separation law has been undertaken to predict the residual strength. Residual stresses due to thermal and swelling strains in the adhesive layer have been included; however their effect on the predicted static strength was not significant. Good agreement was found between the predicted residual strength and the experimental result. [Copyright &y& Elsevier]

Abstract: Experimental and numerical studies have been undertaken on metal laminate (ML) doublers and hybrid fibre-metal (aluminium–Glare) laminate (FML) doublers to investigate their static and fatigue response under tension loading. Inevitably sheets in these laminates butt together and these butts can affect the joint strength. Progressive damage modelling, including the damage in the adhesive bondline, the butt, the metal and the fibre has been undertaken in both static and fatigue loading. This modelling was found to be in good agreement with the experiment data in terms both of the strength and the failure mechanisms. In ML, the butt influenced the static and fatigue response. In hybrid FML, the specimens either have the fibres parallel to the loading direction (spanwise) or perpendicular to the loading direction (chordwise). The spanwise specimen was found to have the highest strength followed by chordwise specimens without butts and finally chordwise specimens with butts. The most critical position for a butt was found to be adjacent to the doubler end. Without butts the static strength for spanwise and chordwise specimens was controlled by the failure in the Glare layer whilst the fatigue failure was precipitated by failure in the aluminium sheet. [Copyright &y& Elsevier]

This paper presents the experimental and numerical investigation of the residual strength of steel-composites joints aged in distilled and salt water under steady and fluctuating conditions at a temperature of 45 °C. The adhesive and the composites adherend had been characterized to obtain water absorption behavior and water-dependent mechanical properties. It was found that under the steady condition, the residual strength of the joints aged in distilled water was lower than that aged in salt water; however, under the fluctuating condition, the residual strength of the joints aged in salt water was lower than that aged in distilled water. Overall, the residual strength of the joints aged in salt water under the fluctuating condition was the lowest. Sequentially water diffusion and progressive damage finite element modeling of the joints considering the failure mode have been undertaken. The predicted residual strengths included the cohesive and interfacial failures were in reasonably agreement with the experimental results. [ABSTRACT FROM AUTHOR]

Type III secretion (T3S) is an essential virulence factor used by Gram-negative pathogenic bacteria to deliver effector proteins into the host cell to establish and maintain an intracellular infection. Chlamydia is known to use T3S to facilitate invasion of host cells but many proteins in the system remain uncharacterized. The C. trachomatis protein CT584 has previously been implicated in T3S. Thus, we analyzed the CT584 ortholog in C. pneumoniae (Cpn0803) and found that it associates with known T3S proteins including the needle-filament protein (CdsF), the ATPase (CdsN), and the C-ring protein (CdsQ). Using membrane lipid strips, Cpn0803 interacted with phosphatidic acid and phosphatidylinositol, suggesting that Cpn0803 may associate with host cells. Crystallographic analysis revealed a unique structure of Cpn0803 with a hydrophobic pocket buried within the dimerization interface that may be important for binding small molecules. Also, the binding domains on Cpn0803 for CdsN, CdsQ, and CdsF were identified using Pepscan epitope mapping. Collectively, these data suggest that Cpn0803 plays a role in T3S. [ABSTRACT FROM AUTHOR]