Structural mechanism for modulation of functional amyloid and biofilm formation by Staphylococcal Bap protein switch.

The Staphylococcal Bap proteins sense environmental signals (such as pH, [Ca2+ ]) to build amyloid scaffold biofilm matrices via unknown mechanisms. We here report the crystal structure of the aggregation-prone region of Staphylococcus aureus Bap which adopts a dumbbell-shaped fold. The middle module (MM) connecting the N-terminal and C-terminal lobes consists of a tandem of novel double-Ca2+ -binding motifs involved in cooperative interaction networks, which undergoes Ca2+ -dependent order-disorder conformational switches. The N-terminal lobe is sufficient to mediate amyloid aggregation through liquid-liquid phase separation and maturation, and subsequent biofilm formation under acidic conditions. Such processes are promoted by disordered MM at low [Ca2+ ] but inhibited by ordered MM stabilized by Ca2+ binding, with inhibition efficiency depending on structural integrity of the interaction networks. These studies illustrate a novel protein switch in pathogenic bacteria and provide insights into the mechanistic understanding of Bap proteins in modulation of functional amyloid and biofilm formation, which could be implemented in the anti-biofilm drug design.

Standardized Tip-Apex Distance (STAD): a modified individualized measurement of cephalic fixator position based on its own femoral head diameter in geriatric intertrochanteric fractures with internal fixation.

OBJECTIVE: To design a standardized Tip-Apex Distance (STAD) and analyze the clinical significance of STAD in predicting cut-out in geriatric intertrochanteric fractures with internal fixation. METHODS: Firstly, we designed STAD according to the rule of TAD. We measured the STAD individually based on its own femoral head diameter (iFHD) instead of the known diameter of the lag screw in calculating TAD, resulting in that the STAD is simply the relative quantitation relationship of iFHD (the times of iFHD). In this study, we assumed that all the iFHD was 6D (1iFHD = 6D, or 1D = 1/6 of iFHD) in order for complete match of the Cleveland zone system, easy comparison of the STAD, and convenient identification for artificial intelligence. Secondly, we calculated and recorded all the STAD of cephalic fixator in 123 eligible ITF patients. Thirdly, we grouped all the ITF patients into the Failure and Non-failure groups according to whether cut-out or not, and analyzed the correlation between the cut-out and the STAD. RESULTS: Cleveland zone, Parker's ratio (AP), TAD, and STAD were associated with the cut-out in univariate analysis. However, only STAD was the independent predictor of the cut-out by multivariate analysis. No cut-out was observed when STAD ≤ 2D (1/3 of iFHD). The Receiver Operating Characteristic (ROC) curve indicated that STAD was a reliable predictor of cut-out, and the best cut-off value of STAD was 2.92D. Cut-out rate increased dramatically when STAD increased, especially when STAD > 3D (1/2 of iFHD). CONCLUSION: Essentially, the STAD is a relative quantitation relationship of iFHD. The STAD is a reliable measurement of cephalic fixator position in predicting cut-out in geriatric ITF patients with single-screw cephalomedullary nail fixations. For avoiding cut-out, the STAD should be no more than a half of iFHD. LEVEL OF EVIDENCE: Level III, Prognostic Study.

Joint Salvage and Biological Repair of Massive-Cavity Bone Defects After Extensive Curettage of Campanacci Grade II or III Giant Cell Tumor Around the Knee With Vascularized Fibular Autograft and Cancellous Allograft.

OBJECTIVE: The aim of the study was to report the clinical outcomes of repair of massive-cavity bone defects after extensive curettage of Campanacci grade II or III giant cell tumor (GCT) around knee with vascularized fibular autograft and cancellous allograft. METHODS: There were 12 consecutive patients with Campanacci grade II or III GCT around knee treated in our department between 2004 and 2016. All the patients underwent clinical evaluation, plain radiography, and/or magnetic resonance imaging of the knee right after admission. To preserve their knee function, we repaired the massive-cavity bone defects after extensive curettage of GCT by vascularized fibular autografts and cancellous allograft. All the patients were evaluated through clinical examinations, plain radiography of the knee and chest, and Musculoskeletal Tumor Society (MSTS) scores of the lower extremity in the follow-ups. RESULTS: The follow-up ranged from 1.5 to 12.0 years (mean, 4.2 years). There were no local recurrences or lung metastasis in any of the 12 patients at the last follow-up. Ten patients had no pain or experienced occasional pain, and 9 were able to resume their previous work. The mean range of motion of knee flexion was 117 degrees, and the extension was -6 degrees. The mean MSTS score was 24.7, and a total of 10 patients had excellent or good MSTS scores. CONCLUSIONS: It is reliable to achieve knee joint salvage and repair massive-cavity bone defects after extensive curettage with vascularized fibular autograft and cancellous allograft in patients with Campanacci grade II or III GCT around the knee.

Repair of Small-Size Wound With Achilles Tendon Exposure With Proximal Pedicled Cutaneous Neurovascular Flap.

OBJECTIVE: To investigate the clinical outcomes associated with repairing of small-sized wounds of Achilles tendon exposure with proximal pedicled cutaneous neurovascular flap in the dorsolateral foot. METHODS: After thorough debridement, 16 cases with small-sized wounds of Achilles tendon exposure were repaired by proximal pedicled cutaneous neurovascular flap of the dorsolateral foot, and their clinical outcomes were observed. RESULTS: All the flaps in the 16 cases survived completely, excluding the marginal part necrosis in 1 case, and all the wounds were healed. The 2-point discrimination of the flaps was 14.53 ± 1.55 mm (range, 12-17 mm) in patients without sural nerve injury after 3 to 18 months follow-up. No discomfort was felt in wearing normal shoes by all the 16 patients. CONCLUSIONS: It is reasonable to repair the small-sized wounds of Achilles tendon exposure with proximal pedicled cutaneous neurovascular flap of dorsolateral foot due to its effective repair of the wound, relatively uncomplicated surgery, and had satisfactory healing recovery.

Distal radius reconstruction with vascularized proximal fibular autograft after en-bloc resection of recurrent giant cell tumor.

BACKGROUND: Giant cell tumors (GCTs) located in the distal radius are likely to recur, and the treatment of such recurrent tumors is very difficult. Here, we report our clinical experience in distal radius reconstruction with vascularized proximal fibular autografts after en-bloc excision of the entire distal radius in 17 patients with recurrent GCT (RGCT) of the distal radius. METHODS: All 17 patients with RGCT in distal radius underwent plain radiography and/or magnetic resonance imaging (MRI) of the distal radius as the initial evaluation after hospitalization. Then the distal radius were replaced by vascularized proximal fibular autografts after en-bloc RGCT resection. We assessed all patients by using clinical examinations, plain radiography of the wrist and chest, and Mayo wrist scores in the follow-ups. RESULTS: After an average follow-up of 4.3 years (range: 1.5-10.0 years), no lung metastasis or local recurrence was detected in any of the 17 patients. In total, 14 patients had excellent or good functional wrist scores, 16 were pain free or had occasional pain, and 15 patients returned to work. The mean range of motion of the wrist was 101° (flexion-extension), and the mean grip strength was 77.2 % of the contralateral normal hand. CONCLUSION: En-bloc excision of the entire distal radius and distal radius reconstruction with a vascularized proximal fibular autograft can effectively achieve local tumor control and preserve wrist function in patients with RGCT of the distal radius.

Fine-tuned h-ferritin nanocage with multiple gold clusters as near-infrared kidney specific targeting nanoprobe.

When stabilized and functionalized by biomolecules, noble metal (such as gold and silver) cluster-based hybrid nanocomposites have shown great promise for biomedical applications, due to their unique physiochemical properties originating from the inorganic elements and specific functionality and biocompatibility from their biological components. Although certain promise for bioimaging, biosensing, and biomimetic catalysis has been demonstrated, it is still a great challenge to integrate the defined functionality of the biomolecules with enhanced or novel physiochemical properties of the metal clusters, under control at the molecular level. Herein, based on molecular dynamics simulation of a gold (Au) cluster assembly, we designed near-infrared (NIR) fluorescent hybrid nanocomposites with multiple Au clusters within an apo H-ferritin (HFt) nanocage. The fluorescence quantum yield of near-infrared (NIR) Au-HFt is about 63.4% and the emission peak is 810 nm. The NIR Au-HFt is one of the first native protein-guided Au cluster-based nanomaterials for in vivo biowindow imaging. In vivo fluorescent imaging and quantification of Au element confirmed that Au-HFt not only retained the kidney targeting properties of HFt well (about 10 times higher Au concentration in kidney than in liver and spleen, the most common organs for nanoparticle accumulation), but also gained strong NIR imaging capability for live animals. The NIR Au-HFt showed powerful tissue penetrating ability, strong fluorescent efficiency, and excellent kidney targeting specificity. These results thus open new opportunities for kidney disease imaging and theranostic applications.

Structural mechanisms for binding and activation of a contact-quenched fluorophore by RhoBAST.

The fluorescent light-up aptamer RhoBAST, which binds and activates the fluorophore-quencher conjugate tetramethylrhodamine-dinitroaniline with high affinity, super high brightness, remarkable photostability, and fast exchange kinetics, exhibits excellent performance in super-resolution RNA imaging. Here we determine the co-crystal structure of RhoBAST in complex with tetramethylrhodamine-dinitroaniline to elucidate the molecular basis for ligand binding and fluorescence activation. The structure exhibits an asymmetric "A"-like architecture for RhoBAST with a semi-open binding pocket harboring the xanthene of tetramethylrhodamine at the tip, while the dinitroaniline quencher stacks over the phenyl of tetramethylrhodamine instead of being fully released. Molecular dynamics simulations show highly heterogeneous conformational ensembles with the contact-but-unstacked fluorophore-quencher conformation for both free and bound tetramethylrhodamine-dinitroaniline being predominant. The simulations also show that, upon RNA binding, the fraction of xanthene-dinitroaniline stacked conformation significantly decreases in free tetramethylrhodamine-dinitroaniline. This highlights the importance of releasing dinitroaniline from xanthene tetramethylrhodamine to unquench the RhoBAST-tetramethylrhodamine-dinitroaniline complex. Using SAXS and ITC, we characterized the magnesium dependency of the folding and binding mode of RhoBAST in solution and indicated its strong structural robustness. The structures and binding modes of relevant fluorescent light-up aptamers are compared, providing mechanistic insights for rational design and optimization of this important fluorescent light-up aptamer-ligand system.

Modified classification and single-stage microsurgical repair of posttraumatic infected massive bone defects in lower extremities.

Posttraumatic infected massive bone defects in lower extremities are difficult to repair because they frequently exhibit massive bone and/or soft tissue defects, serious bone infection, and excessive scar proliferation. This study aimed to determine whether these defects could be classified and repaired at a single stage. A total of 51 cases of posttraumatic infected massive bone defect in lower extremity were included in this study. They were classified into four types on the basis of the conditions of the bone defects, soft tissue defects, and injured limb length, including Type A (without soft tissue defects), Type B (with soft tissue defects of 10 × 20 cm or less), Type C (with soft tissue defects of 10 × 20 cm or more), and Type D (with the limb shortening of 3 cm or more). Four types of single-stage microsurgical repair protocols were planned accordingly and implemented respectively. These protocols included the following: Protocol A, where vascularized fibular graft was implemented for Type A; Protocol B, where vascularized fibular osteoseptocutaneous graft was implemented for Type B; Protocol C, where vascularized fibular graft and anterior lateral thigh flap were used for Type C; and Protocol D, where limb lengthening and Protocols A, B, or C were used for Type D. There were 12, 33, 4, and 2 cases of Types A, B, C, and D, respectively, according to this classification. During the surgery, three cases of planned Protocol B had to be shifted into Protocol C; however, all microsurgical repairs were completed. With reference to Johner-Wruhs evaluation method, the total percentage of excellent and good results was 82.35% after 6 to 41 months of follow-up. It was concluded that posttraumatic massive bone defects could be accurately classified into four types on the basis of the conditions of bone defects, soft tissue coverage, and injured limb length, and successfully repaired with the single-stage repair protocols after thorough debridement.

A single preoperative low-dose dexamethasone may reduce the incidence and severity of postoperative delirium in the geriatric intertrochanteric fracture patients with internal fixation surgery: an exploratory analysis of a randomized, placebo-controlled trial.

OBJECTIVE: Postoperative delirium (POD) is a common complication along with poor prognosis in geriatric intertrochanteric fracture (ITF) patients. However, the prevention and treatment of POD remain unclear. Previous studies have confirmed that POD is essentially a consequence of neuro-inflammatory responses. Dexamethasone is a glucocorticoid with comprehensive anti-inflammatory effects, while a high dose of dexamethasone correlates with many side effects or even adverse consequences. Thus, this prospective study aims to discuss whether a single preoperative low-dose dexamethasone can reduce the impact of POD on geriatric ITF patients with internal fixation surgery. METHODS: Between June 2020 and October 2022, there were 219 consecutive ITF patients assessed in our department. Of the 219 ITF patients, 160 cases who met the inclusion and exclusion criteria were finally enrolled and randomly allocated to the dexamethasone group and the placebo group (80 geriatric ITF patients in each group) in this prospective study. The patients in the dexamethasone group received intravenous 10 mg (2 ml) dexamethasone while the patients in the placebo group received intravenous 2 ml saline in 30 min before being sent to the operating room, respectively. The baseline characteristics, surgical information, incidence and severity of POD as the efficacy-related outcomes, and infection events and hyperglycemia as safety-related outcomes (adverse events), were collected and analyzed between the two groups. The severity of POD was evaluated by Memorial Delirium Assessment Scale (MDAS) score. RESULTS: There were no differences in baseline characteristics and surgical information between the dexamethasone group and the placebo group. The dexamethasone group had a lower incidence of POD than the placebo group within the first 5 days after surgery [(9/80, 11.3% vs. 21/80, 26.3%, RR = 0.83, 95% CI 0.71-0.97, P = 0.015]. The dexamethasone group had lower MDAS scores (Mean ± SD) than the placebo group [13.2 ± 1.0 (range 11 to 15) vs. 15.48 ± 2.9 (range 9 to 20), P = 0.011, effect size = 0.514]. There were no differences in infection events and hyperglycemia between the two groups. CONCLUSIONS: A single preoperative low-dose dexamethasone may reduce the incidence and severity of POD in geriatric ITF patients with internal fixation surgery. TRIAL REGISTRATION: ChiCTR2200055281.

Structural and dynamic mechanisms for coupled folding and tRNA recognition of a translational T-box riboswitch.

T-box riboswitches are unique riboregulators where gene regulation is mediated through interactions between two highly structured RNAs. Despite extensive structural insights, how RNA-RNA interactions drive the folding and structural transitions of T-box to achieve functional conformations remains unclear. Here, by combining SAXS, single-molecule FRET and computational modeling, we elaborate the folding energy landscape of a translational T-box aptamer consisting of stems I, II and IIA/B, which Mg2+-induced global folding and tRNA binding are cooperatively coupled. smFRET measurements reveal that high Mg2+ stabilizes IIA/B and its stacking on II, which drives the pre-docking of I and II into a competent conformation, subsequent tRNA binding promotes docking of I and II to form a high-affinity tRNA binding groove, of which the essentiality of IIA/B and S-turn in II is substantiated with mutational analysis. We highlight a delicate balance among Mg2+, the intra- and intermolecular RNA-RNA interactions in modulating RNA folding and function.

The impact of preoperative single low-dose dexamethasone on in-hospital prognosis in geriatric intertrochanteric fracture patients: Analysis of secondary outcomes in a randomized controlled trial.

BACKGROUND: Intertrochanteric fracture in the geriatric population is associated with poor prognosis, which may be attributed to consistent stress and the systemic inflammatory response. Dexamethasone is an exogenous glucocorticoid commonly used in clinical practice for broad anti-inflammatory action. The purpose is to investigate whether a single preoperative low-dose dexamethasone can improve the in-hospital prognosis in geriatric intertrochanteric fracture patients undergoing internal fixation surgery. METHODS: Between June 2020 and October 2022, 219 eligible patients with intertrochanteric fractures were in this study. After meeting the inclusion and exclusion criteria, 160 patients were randomly allocated to the dexamethasone or placebo groups (80 patients who are geriatric with an intertrochanteric fracture in each group). The patients in the dexamethasone group received 10 mg (2 mL) of dexamethasone intravenously, whereas the patients in the placebo group received 2 mL of saline intravenously within 30 minutes before being sent to the operating room. The efficacy-related outcomes (the first bed-chair transfer ability, in-hospital mortality, and length of stay) and safety-related outcomes (infection events and hyperglycemia) were collected for analysis. RESULTS: There were no significant differences in the baseline characteristics between the 2 groups. The dexamethasone group had a significantly higher rate of the first bed-chair transfer than the placebo group (65.0% [52/80] vs 48.8% [39/80], relative risk = 1.46, 95% confidence interval = 1.02 to 2.11; P = .038). One patient in the dexamethasone group and 7 patients in the placebo group died during hospitalization (1.3% [1/80] vs 8.8% [7/80], relative risk = 0.92, 95% confidence interval = 0.86 to 0.99; P = .07). No differences were found in the length of stay, infections, and hyperglycemia between the 2 groups. CONCLUSION: A single preoperative low-dose of dexamethasone can improve the in-hospital prognosis (increase the ability of the first bed-chair transfer and potentially decrease the in-hospital mortality) in geriatric intertrochanteric fracture patients after internal fixation surgery.

Zika virus RNA structure controls its unique neurotropism by bipartite binding to Musashi-1.

Human RNA binding protein Musashi-1 (MSI1) plays a critical role in neural progenitor cells (NPCs) by binding to various host RNA transcripts. The canonical MSI1 binding site (MBS), A/GU(1-3)AG single-strand motif, is present in many RNA virus genomes, but only Zika virus (ZIKV) genome has been demonstrated to bind MSI1. Herein, we identified the AUAG motif and the AGAA tetraloop in the Xrn1-resistant RNA 2 (xrRNA2) as the canonical and non-canonical MBS, respectively, and both are crucial for ZIKV neurotropism. More importantly, the unique AGNN-type tetraloop is evolutionally conserved, and distinguishes ZIKV from other known viruses with putative MBSs. Integrated structural analysis showed that MSI1 binds to the AUAG motif and AGAA tetraloop of ZIKV in a bipartite fashion. Thus, our results not only identified an unusual viral RNA structure responsible for MSI recognition, but also revealed a role for the highly structured xrRNA in controlling viral neurotropism.

The correlation between cutout and eccentric distance (ED) of the cephalic fixator tip in geriatric intertrochanteric fractures with internal fixation.

BACKGROUND: The location of cephalic fixator tip with different eccentric distance (ED) should have different risks of cutout. This study aims to evaluate the cephalic fixator tip position by measuring ED of the cephalic fixator tip in geriatric ITF patients with single-screw cephalomedullary nail (SCMN) fixation and analyze the correlation between the cutout and the ED. METHODS: Firstly, we assumed all the femoral head was a regular sphere and standardized the radius of the femoral head (RFD) as "3" no matter how big the RFD was for complete match of the Cleveland zone system and convenient identification of artificial intelligence. Secondly, we measured the ED of the cephalic fixator tip by calculating the distances from the cephalic fixator tip to the geometric central axis of the femoral neck and head on both AP view and lateral view radiographs. Thirdly, we evaluated all the ED of the cephalic fixator tip in the eligible 123 geriatric ITF patients and analyzed the correlation between the cutout and the ED. RESULTS: The ED in cutout group (1.25 ± 0.43) is much bigger than that in non-cutout group (0.64 ± 0.34) with significant difference (OR = 50.01, 95% CI 8.42-297.19, p < 0.001). The probability of cutout increased with ED increasing, especially when "ED ≥ 1." The best cutoff value of ED for predicting cutout was "1.022" ("1.022" was just a little bit more than 1/3 times of RFD because "RFD = 3," sensitivity = 73.3%, specificity = 86.1%, and AUC = 0.867, p < 0.001). CONCLUSION: ED is suitable for evaluation of the cephalic fixator tip position for predicting cutout in geriatric ITF patients with SCMN fixation, and ED can potentially be used as artificial intelligence application during surgery. The smaller the ED, the lower the cutout rate. For avoiding cutout, the ED of the cephalic fixator tip should be less than one-third times of the radius of the femoral head.

Eccentric distance zone analysis system: New regional evaluation of cephalic fixator tip location for predicting cut-out in geriatric intertrochanteric fractures with internal fixation.

Objective: The aim of this study was to investigate an eccentric distance (ED) zone analysis system for regional evaluation of the cephalic fixator tip based on the ED of the cephalic fixator tip referenced to the radius of its own femoral head to predict cut-out in intertrochanteric fractures (ITF) with internal fixation. Methods: First, we assumed all the femoral heads were regular spheres with the radius (R FD) of "3" for a complete match of the Cleveland zone system and calculated the ED of the cephalic fixator tip by measuring the distances from the cephalic fixator tip to the geometric central axis in the femoral neck and head on both anteroposterior (AP) view and lateral view radiographs. Second, we defined the maximum transverse section of the femoral head into three zones named ED Zone A with ED less than "1," Zone B with ED ranging in "1-2," and Zone C with ED ranging in "2-3" in turns by concentric circles (circles A, B, and C) with the radius of 1/3, 2/3, and 3/3 times of R FD, respectively. Third, we evaluated the ED zones according to the ED and location of the cephalic fixator tip in the eligible 123 ITF patients with single-screw cephalomedullary nail (SCMN) fixation and then analyzed the correlation between the cut-out rate and the ED zones. Results: The cut-out rates in ED Zones A, B, and C were 4.17%, 38.46%, and 100%, respectively. Multivariate logistic regression indicated that ED Zone A had at least a 14 times lower rate of cut-out compared with ED Zone B. The cephalic fixator tip located in ED Zone A has a lower cut-out rate than that in Cleveland Zone 5. The cut-out rate in ED Zone A is significantly lower than that in the region inside Cleveland Zone 5 but outside ED Zone A. Conclusion: ED zone analysis system is a reliable regional evaluation of the cephalic fixator tip position for predicting cut-out in geriatric ITF patients with SCMN fixations and potentially an artificial intelligence measurement during surgery. For decreasing the cut-out rate, the cephalic fixator tip should be located in ED Zone A.

Surgical Position of Lateral-Tilted Supine is Suitable for Proximal Humeral Fracture Operations in Geriatric Patients.

Objective: To report a new surgical position of lateral-tilted supine (LTS) for geriatric proximal humeral fracture operations. Methods: Between January 2016 and December 2020, we adopted the LTS position for operations in 65 geriatric patients with proximal humeral fractures. Results: Sixty-five patients including 25 males and 40 females aged 80.3 ± 8.5 years. The LTS position could be used for almost all proximal humeral fracture surgeries, such as ORIF with plate, suture anchor, and other fixation in 4 patients, open reduction and internal fixation (ORIF) with multiLoc nailing in 48, and shoulder hemiarthroplasty (SHA) in 13. Surgical position setting times were 11.47 ± 2.14 min. The systolic blood pressure changes before and after positioning were 15.07 ± 8.72 mmHg. All of the C-arm X-ray directions, including the cephalic side, contralateral side, and ipsilateral side, can be used in the LTS position surgeries. No surgical complications or no surgical position-related complications were found in these 65 cases. Conclusion: The surgical position of LTS is suitable for geriatric proximal humeral fracture operations.

The Correlation Between Timing of Surgery and the Need for RBC Transfusions in the Geriatric Intertrochanteric Fracture Population.

OBJECTIVE: To identify whether the timing of surgery affects red blood cell (RBC) transfusion requirements in the elderly with intertrochanteric fractures. METHODS: We retrospectively studied all patients undergoing surgical fixation of their intertrochanteric fractures in our hospital between January 2009 and December 2018 and analyzed the relationship between the timing of surgery and RBC transfusion. RESULTS: A total of 679 patients were included in this study. The need for RBC transfusion was lower in the patients who underwent surgery within 12 h after admission (timing of surgery <12 h, <12 h group) than those who underwent surgery over 12 h after admission (timing of surgery >12 h, >12 h group) (P = 0.046); lower in the the patients who underwent surgery within 24 h after admission (timing of surgery <24 h, <24 h group) than in those who underwent surgery over 24 h after admission (timing of surgery >24 h, >24 h group) (P = 0.008), and lower in the <24 h group compared to the patients who underwent surgery within 48 h after admission (timing of surgery <48 h, <48 h group) (P = 0.035). Moreover, the need for RBC transfusion was lower in the <24 h group (in the first 24 h from admission to surgery) than in the 24-48 h group (in the second 24 h from admission to surgery) (P = 0.016), and also lower in the <24 h group compared to the 48-72 h group (in the third 24 h from admission to surgery) (P = 0.047). However, there were no differences between the <12 h group and 12-24 h group, between the <12 h group and <24 h group, and between the 12-24 h group and <24 h group, respectively. CONCLUSION: Timing of surgery within 24 h contributes to the reduction of RBC transfusion in the elderly with intertrochanteric fractures.

Homeochronous usage of structural bone allografts with vascularized fibular autografts for biological repair of massive bone defects in the lower extremities after bone tumor excision.

We report the clinical outcomes of homeochronous usage of massive bone allografts with vascularized fibular autografts for the biological repair of lower-extremity bone defects secondary to bone tumor excision. Large bone defects in the lower extremities of 17 patients (10 men and seven women; age range, 6 to 34 years) who underwent bone tumor excision were repaired using massive bone allografts along with vascularized fibular autografts. After 6 to 48 months (mean, 20.2 months) of follow-up, the wounds at the donor and recipient sites healed in one stage, the monitoring flaps remained viable, the immune response to the massive bone allografts was minimal, and there were no complications in the donor limbs. Of the 17 patients, 13 and 3 cases showed radiographic union in 6 months and 8 months after surgery, respectively; one case of malignant synovioma showed recurrence, and therefore, leg amputation was performed 2.5 months after surgery. None of the massive bone allografts were absorbed or fractured at the last follow-up. The Mankin evaluation rating was excellent in eight cases, good in five cases, fair in two cases, and poor in two cases; the total rate of excellent and good cases was 76.47%. Homeochronous usage of massive bone allografts with vascularized fibular autografts is a satisfactory method for the biological repair of massive bone defects in the lower limbs after bone tumor excision.

Molecular mechanisms underlying the extreme mechanical anisotropy of the flaviviral exoribonuclease-resistant RNAs (xrRNAs).

Mechanical anisotropy is an essential property for many biomolecules to assume their structures, functions and applications, however, the mechanisms for their direction-dependent mechanical responses remain elusive. Herein, by using a single-molecule nanopore sensing technique, we explore the mechanisms of directional mechanical stability of the xrRNA1 RNA from ZIKA virus (ZIKV), which forms a complex ring-like architecture. We reveal extreme mechanical anisotropy in ZIKV xrRNA1 which highly depends on Mg2+ and the key tertiary interactions. The absence of Mg2+ and disruption of the key tertiary interactions strongly affect the structural integrity and attenuate mechanical anisotropy. The significance of ring structures in RNA mechanical anisotropy is further supported by steered molecular dynamics simulations in combination with force distribution analysis. We anticipate the ring structures can be used as key elements to build RNA-based nanostructures with controllable mechanical anisotropy for biomaterial and biomedical applications.

Directional mechanical stability of Bacteriophage φ29 motor's 3WJ-pRNA: Extraordinary robustness along portal axis.

The molecular motor exploited by bacteriophage φ29 to pack DNA into its capsid is regarded as one of the most powerful mechanical devices present in viral, bacterial, and eukaryotic systems alike. Acting as a linker element, a prohead RNA (pRNA) effectively joins the connector and ATPase (adenosine triphosphatase) components of the φ29 motor. During DNA packing, this pRNA needs to withstand enormous strain along the capsid's portal axis-how this remarkable stability is achieved remains to be elucidated. We investigate the mechanical properties of the φ29 motor's three-way junction (3WJ)-pRNA using a combined steered molecular dynamics and atomic force spectroscopy approach. The 3WJ exhibits strong resistance to stretching along its coaxial helices, demonstrating its super structural robustness. This resistance disappears, however, when external forces are applied to the transverse directions. From a molecular standpoint, we demonstrate that this direction-dependent stability can be attributed to two Mg clamps that cooperate and generate mechanical resistance in the pRNA's coaxial direction. Our results suggest that the asymmetric nature of the 3WJ's mechanical stability is entwined with its biological function: Enhanced rigidity along the portal axis is likely essential to withstand the strain caused by DNA condensation, and flexibility in other directions should aid in the assembly of the pRNA and its association with other motor components.

Sequential protein unfolding through a carbon nanotube pore.

An assortment of biological processes, like protein degradation and the transport of proteins across membranes, depend on protein unfolding events mediated by nanopore interfaces. In this work, we exploit fully atomistic simulations of an artificial, CNT-based nanopore to investigate the nature of ubiquitin unfolding. With one end of the protein subjected to an external force, we observe non-canonical unfolding behaviour as ubiquitin is pulled through the pore opening. Secondary structural elements are sequentially detached from the protein and threaded into the nanotube, interestingly, the remaining part maintains native-like characteristics. The constraints of the nanopore interface thus facilitate the formation of stable "unfoldon" motifs above the nanotube aperture that can exist in the absence of specific native contacts with the other secondary structure. Destruction of these unfoldons gives rise to distinct force peaks in our simulations, providing us with a sensitive probe for studying the kinetics of serial unfolding events. Our detailed analysis of nanopore-mediated protein unfolding events not only provides insight into how related processes might proceed in the cell, but also serves to deepen our understanding of structural arrangements which form the basis for protein conformational stability.