Inhibition of basal FGF receptor signaling by dimeric Grb2.

Receptor tyrosine kinase activity is known to occur in the absence of extracellular stimuli. Importantly, this "background" level of receptor phosphorylation is insufficient to effect a downstream response, suggesting that strict controls are present and prohibit full activation. Here a mechanism is described in which control of FGFR2 activation is provided by the adaptor protein Grb2. Dimeric Grb2 binds to the C termini of two FGFR2 molecules. This heterotetramer is capable of a low-level receptor transphosphorylation, but C-terminal phosphorylation and recruitment of signaling proteins are sterically hindered. Upon stimulation, FGFR2 phosphorylates tyrosine residues on Grb2, promoting dissociation from the receptor and allowing full activation of downstream signaling. These observations establish a role for Grb2 as an active regulator of RTK signaling.

Incidence and imaging characteristics of difficult to detect retrospectively identified brain metastases in patients receiving repeat courses of stereotactic radiosurgery.

PURPOSE: During stereotactic radiosurgery (SRS) planning for brain metastases (BM), brain MRIs are reviewed to select appropriate targets based on radiographic characteristics. Some BM are difficult to detect and/or definitively identify and may go untreated initially, only to become apparent on future imaging. We hypothesized that in patients receiving multiple courses of SRS, reviewing the initial planning MRI would reveal early evidence of lesions that developed into metastases requiring SRS. METHODS: Patients undergoing two or more courses of SRS to BM within 6 months between 2016 and 2018 were included in this single-institution, retrospective study. Brain MRIs from the initial course were reviewed for lesions at the same location as subsequently treated metastases; if present, this lesion was classified as a "retrospectively identified metastasis" or RIM. RIMs were subcategorized as meeting or not meeting diagnostic imaging criteria for BM (+ DC or -DC, respectively). RESULTS: Among 683 patients undergoing 923 SRS courses, 98 patients met inclusion criteria. There were 115 repeat courses of SRS, with 345 treated metastases in the subsequent course, 128 of which were associated with RIMs found in a prior MRI. 58% of RIMs were + DC. 17 (15%) of subsequent courses consisted solely of metastases associated with + DC RIMs. CONCLUSION: Radiographic evidence of brain metastases requiring future treatment was occasionally present on brain MRIs from prior SRS treatments. Most RIMs were + DC, and some subsequent SRS courses treated only + DC RIMs. These findings suggest enhanced BM detection might enable earlier treatment and reduce the need for additional SRS.

Common sequence motifs of nascent chains engage the ribosome surface and trigger factor.

In the cell, the conformations of nascent polypeptide chains during translation are modulated by both the ribosome and its associated molecular chaperone, trigger factor. The specific interactions that underlie these modulations, however, are still not known in detail. Here, we combine protein engineering, in-cell and in vitro NMR spectroscopy, and molecular dynamics simulations to explore how proteins interact with the ribosome during their biosynthesis before folding occurs. Our observations of α-synuclein nascent chains in living Escherichia coli cells reveal that ribosome surface interactions dictate the dynamics of emerging disordered polypeptides in the crowded cytosol. We show that specific basic and aromatic motifs drive such interactions and directly compete with trigger factor binding while biasing the direction of the nascent chain during its exit out of the tunnel. These results reveal a structural basis for the functional role of the ribosome as a scaffold with holdase characteristics and explain how handover of the nascent chain to specific auxiliary proteins occurs among a host of other factors in the cytosol.

Independent Monte Carlo dose calculation identifies single isocenter multi-target radiosurgery targets most likely to fail pre-treatment measurement.

PURPOSE: For individual targets of single isocenter multi-target (SIMT) Stereotactic radiosurgery (SRS), we assess dose difference between the treatment planning system (TPS) and independent Monte Carlo (MC), and demonstrate persistence into the pre-treatment Quality Assurance (QA) measurement. METHODS: Treatment plans from 31 SIMT SRS patients were recalculated in a series of scenarios designed to investigate sources of discrepancy between TPS and independent MC. Targets with > 5% discrepancy in DMean[Gy] after progressing through all scenarios were measured with SRS MapCHECK. A matched pair analysis was performed comparing SRS MapCHECK results for these targets with matched targets having similar characteristics (volume & distance from isocenter) but no such MC dose discrepancy. RESULTS: Of 217 targets analyzed, individual target mean dose (DMean[Gy]) fell outside a 5% threshold for 28 and 24 targets before and after removing tissue heterogeneity effects, respectively, while only 5 exceeded the threshold after removing effect of patient geometry (via calculation on StereoPHAN geometry). Significant factors affecting agreement between the TPS and MC included target distance from isocenter (0.83% decrease in DMean[Gy] per 2 cm), volume (0.15% increase per cc), and degree of plan modulation (0.37% increase per 0.01 increase in modulation complexity score). SRS MapCHECK measurement had better agreement with MC than with TPS (2%/1 mm / 10% threshold gamma pass rate (GPR) = 99.4 ± 1.9% vs. 93.1 ± 13.9%, respectively). In the matched pair analysis, targets exceeding 5% for MC versus TPS also had larger discrepancies between TPS and measurement with no GPR (2%/1 mm / 10% threshold) exceeding 90% (71.5% ± 16.1%); whereas GPR was high for matched targets with no such MC versus TPS difference (96.5% ± 3.3%, p = 0.01). CONCLUSIONS: Independent MC complements pre-treatment QA measurement for SIMT SRS by identifying problematic individual targets prior to pre-treatment measurement, thus enabling plan modifications earlier in the planning process and guiding selection of targets for pre-treatment QA measurement.

Development of consensus-driven SPIRIT and CONSORT extensions for early phase dose-finding trials: the DEFINE study.

BACKGROUND: Early phase dose-finding (EPDF) trials are crucial for the development of a new intervention and influence whether it should be investigated in further trials. Guidance exists for clinical trial protocols and completed trial reports in the SPIRIT and CONSORT guidelines, respectively. However, both guidelines and their extensions do not adequately address the characteristics of EPDF trials. Building on the SPIRIT and CONSORT checklists, the DEFINE study aims to develop international consensus-driven guidelines for EPDF trial protocols (SPIRIT-DEFINE) and reports (CONSORT-DEFINE). METHODS: The initial generation of candidate items was informed by reviewing published EPDF trial reports. The early draft items were refined further through a review of the published and grey literature, analysis of real-world examples, citation and reference searches, and expert recommendations, followed by a two-round modified Delphi process. Patient and public involvement and engagement (PPIE) was pursued concurrently with the quantitative and thematic analysis of Delphi participants' feedback. RESULTS: The Delphi survey included 79 new or modified SPIRIT-DEFINE (n = 36) and CONSORT-DEFINE (n = 43) extension candidate items. In Round One, 206 interdisciplinary stakeholders from 24 countries voted and 151 stakeholders voted in Round Two. Following Round One feedback, one item for CONSORT-DEFINE was added in Round Two. Of the 80 items, 60 met the threshold for inclusion (≥ 70% of respondents voted critical: 26 SPIRIT-DEFINE, 34 CONSORT-DEFINE), with the remaining 20 items to be further discussed at the consensus meeting. The parallel PPIE work resulted in the development of an EPDF lay summary toolkit consisting of a template with guidance notes and an exemplar. CONCLUSIONS: By detailing the development journey of the DEFINE study and the decisions undertaken, we envision that this will enhance understanding and help researchers in the development of future guidelines. The SPIRIT-DEFINE and CONSORT-DEFINE guidelines will allow investigators to effectively address essential items that should be present in EPDF trial protocols and reports, thereby promoting transparency, comprehensiveness, and reproducibility. TRIAL REGISTRATION: SPIRIT-DEFINE and CONSORT-DEFINE are registered with the EQUATOR Network ( https://www.equator-network.org/ ).

Identification of RNA Base Pairs and Complete Assignment of Nucleobase Resonances by Proton-Detected Solid-State NMR Spectroscopy at 100†kHz MAS.

Knowledge of RNA structure, either in isolation or in complex, is fundamental to understand the mechanism of cellular processes. Solid-state NMR (ssNMR) is applicable to high molecular-weight complexes and does not require crystallization; thus, it is well-suited to study RNA as part of large multicomponent assemblies. Recently, we solved the first structures of both RNA and an RNA-protein complex by ssNMR using conventional 13 C- and 15 N-detection. This approach is limited by the severe overlap of the RNA peaks together with the low sensitivity of multidimensional experiments. Here, we overcome the limitations in sensitivity and resolution by using 1 H-detection at fast MAS rates. We develop experiments that allow the identification of complete nucleobase spin-systems together with their site-specific base pair pattern using sub-milligram quantities of one uniformly labelled RNA sample. These experiments provide rapid access to RNA secondary structure by ssNMR in protein-RNA complexes of any size.

Current multidisciplinary management of brain metastases.

Brain metastasis (BM), the most common adult brain tumor, develops in 20% to 40% of patients with late-stage cancer and traditionally are associated with a poor prognosis. The management of patients with BM has become increasingly complex because of new and emerging systemic therapies and advancements in radiation oncology and neurosurgery. Current therapies include stereotactic radiosurgery, whole-brain radiation therapy, surgical resection, laser-interstitial thermal therapy, systemic cytotoxic chemotherapy, targeted agents, and immune-checkpoint inhibitors. Determining the optimal treatment for a specific patient has become increasingly individualized, emphasizing the need for multidisciplinary discussions of patients with BM. Recognizing and addressing the sequelae of BMs and their treatment while maintaining quality of life and neurocognition is especially important because survival for patients with BMs has improved. The authors present current and emerging treatment options for patients with BM and suggest approaches for managing sequelae and disease recurrence.

Patterns of relapse after successful completion of initial therapy in primary central nervous system lymphoma: a case series.

PURPOSE: Primary central nervous system lymphoma (PCNSL) is a subtype of non-Hodgkin's lymphoma that involves the brain, spinal cord, or leptomeninges, without evidence of systemic disease. This rare disease accounts for ~ 3% of all primary central nervous system (CNS) tumors. Methotrexate-based regimens are the standard of care for this disease with overall survival rates ranging from 14 to 55 months. Relapse after apparent complete remission can occur. We sought to understand the outcomes of patients who relapsed. METHODS: This is an IRB-approved investigation of patients treated at our institution between 12/31/2004 and 10/12/2016. We retrospectively identified all cases of PCNSL as part of a database registry and evaluated these cases for demographic information, absence or presence of relapse, location of relapse, treatment regimens, and median relapse-free survival. RESULTS: This analysis identified 44 patients with a pathologically confirmed diagnosis of PCNSL. Mean age at diagnosis was 63.1 years (range 20-86, SD = 13.2 years). Of the 44 patients, 28 patients successfully completed an initial treatment regimen without recurrence or toxicity that required a change in therapy. Relapse occurred in 11 patients with the location of relapse being in the CNS only (n = 5), vitreous fluid only (n = 1), outside CNS only (n = 3), or a combination of CNS and outside of the CNS (n = 2). Sites of relapse outside of the CNS included testes (n = 1), lung (n = 1), adrenal gland (n = 1), kidney/adrenal gland (n = 1), and retroperitoneum (n = 1). Median relapse-free survival after successful completion of therapy was 6.7 years (95% CI 1.1, 12.6). CONCLUSION: After successful initial treatment, PCNSL has a propensity to relapse, and this relapse can occur both inside and outside of the CNS. Vigilant monitoring of off-treatment patients with a history of PCNSL is necessary to guide early diagnosis of relapse and to initiate aggressive treatment.

Structural characterization of the Asf1-Rtt109 interaction and its role in histone acetylation.

Acetylation of histone H3 at lysine-56 by the histone acetyltransferase Rtt109 in lower eukaryotes is important for maintaining genomic integrity and is required for C. albicans pathogenicity. Rtt109 is activated by association with two different histone chaperones, Vps75 and Asf1, through an unknown mechanism. Here, we reveal that the Rtt109 C-terminus interacts directly with Asf1 and elucidate the structural basis of this interaction. In addition, we find that the H3 N-terminus can interact via the same interface on Asf1, leading to a competition between the two interaction partners. This, together with the recruitment and position of the substrate, provides an explanation of the role of the Rtt109 C-terminus in Asf1-dependent Rtt109 activation.

Retrospective quality metrics review of stereotactic radiosurgery plans treating multiple targets using single-isocenter volumetric modulated arc therapy.

PURPOSE: To characterize key plan quality metrics in multi-target stereotactic radiosurgery (SRS) plans treated using single-isocenter volumetric modulated arc therapy (VMAT) in comparison to dynamic conformal arc (DCA) plans treating single target. To investigate the feasibility of quality improvement in VMAT planning based on previous planning knowledge. MATERIALS AND METHODS: 97 VMAT plans of multi-target and 156 DCA plans of single-target treated in 2017 at a single institution were reviewed. A total of 605 targets were treated with these SRS plans. The prescription dose was normalized to 20 Gy in all plans for this analysis. Two plan quality metrics, target conformity index (CI) and normal tissue volume receiving more than 12 Gy (V12Gy), were calculated for each target. The distribution of V12Gy per target was plotted as a function of the target volume. For multi-target VMAT plans, the number of targets being treated in the same plan and the distance between targets were calculated to evaluate their impact on V12Gy. VMAT plans that had a large deviation of V12Gy from the average level were re-optimized to determine the possibility of reducing the variation of V12Gy in VMAT planning. RESULTS: Conformity index of multi-target VMAT plans were lower than that of DCA plans while the mean values of 12 Gy were comparable. The V12Gy for a target in VMAT plan did not show apparent dependence on the total number of targets or the distance between targets. The distribution of V12Gy exhibited a larger variation in VMAT plans compared to DCA plans. Re-optimization of outlier plans reduced V12 Gy by 33.9% and resulted in the V12Gy distribution in VMAT plans more closely resembling that of DCA plans. CONCLUSION: The benchmark data on key plan quality metrics were established for single-isocenter multi-target SRS planning. It is feasible to use this knowledge to guide VMAT planning and reduce high V12Gy outliers.

Structural characterization of the interaction of α-synuclein nascent chains with the ribosomal surface and trigger factor.

The ribosome is increasingly becoming recognized as a key hub for integrating quality control processes associated with protein biosynthesis and cotranslational folding (CTF). The molecular mechanisms by which these processes take place, however, remain largely unknown, in particular in the case of intrinsically disordered proteins (IDPs). To address this question, we studied at a residue-specific level the structure and dynamics of ribosome-nascent chain complexes (RNCs) of α-synuclein (αSyn), an IDP associated with Parkinson's disease (PD). Using solution-state nuclear magnetic resonance (NMR) spectroscopy and coarse-grained molecular dynamics (MD) simulations, we find that, although the nascent chain (NC) has a highly disordered conformation, its N-terminal region shows resonance broadening consistent with interactions involving specific regions of the ribosome surface. We also investigated the effects of the ribosome-associated molecular chaperone trigger factor (TF) on αSyn structure and dynamics using resonance broadening to define a footprint of the TF-RNC interactions. We have used these data to construct structural models that suggest specific ways by which emerging NCs can interact with the biosynthesis and quality control machinery.

Management of GBM: a problem of local recurrence.

Forty years ago, adjuvant treatment of patients with GBM using fractionated radiotherapy following surgery was shown to substantially improve survival compared to surgery alone. However, even with the addition of temozolomide to radiotherapy, overall survival is quite limited and local failure remains a fundamental problem, despite multiple attempts to increase dose to the tumor target. This review presents the historical background and clinical rationale leading to the current standard of care consisting of 60 Gy total dose in 2 Gy fractions to the MRI-defined targets in younger, high performance status patients and more hypofractionated regimens in elderly and/or debilitated patients. Particle therapies offer the potential to increase local control while reducing dose and, potentially, long-term neurocognitive toxicity. However, improvements in systemic therapies for GBM will need to be implemented before the full benefits of improved local control can be realized.

Relationship of Bacterial Richness to Organic Degradation Rate and Sediment Age in Subseafloor Sediment.

UNLABELLED: Subseafloor sediment hosts a large, taxonomically rich, and metabolically diverse microbial ecosystem. However, the factors that control microbial diversity in subseafloor sediment have rarely been explored. Here, we show that bacterial richness varies with organic degradation rate and sediment age. At three open-ocean sites (in the Bering Sea and equatorial Pacific) and one continental margin site (Indian Ocean), richness decreases exponentially with increasing sediment depth. The rate of decrease in richness with increasing depth varies from site to site. The vertical succession of predominant terminal electron acceptors correlates with abundance-weighted community composition but does not drive the vertical decrease in richness. Vertical patterns of richness at the open-ocean sites closely match organic degradation rates; both properties are highest near the seafloor and decline together as sediment depth increases. This relationship suggests that (i) total catabolic activity and/or electron donor diversity exerts a primary influence on bacterial richness in marine sediment and (ii) many bacterial taxa that are poorly adapted for subseafloor sedimentary conditions are degraded in the geologically young sediment, where respiration rates are high. Richness consistently takes a few hundred thousand years to decline from near-seafloor values to much lower values in deep anoxic subseafloor sediment, regardless of sedimentation rate, predominant terminal electron acceptor, or oceanographic context. IMPORTANCE: Subseafloor sediment provides a wonderful opportunity to investigate the drivers of microbial diversity in communities that may have been isolated for millions of years. Our paper shows the impact of in situ conditions on bacterial community structure in subseafloor sediment. Specifically, it shows that bacterial richness in subseafloor sediment declines exponentially with sediment age, and in parallel with organic-fueled oxidation rate. This result suggests that subseafloor diversity ultimately depends on electron donor diversity and/or total community respiration. This work studied how and why biological richness changes over time in the extraordinary ecosystem of subseafloor sediment.

Solution structure of the major factor VIII binding region on von Willebrand factor.

Although much of the function of von Willebrand factor (VWF) has been revealed, detailed insight into the molecular structure that enables VWF to orchestrate hemostatic processes, in particular factor VIII (FVIII) binding and stabilization in plasma, is lacking. Here, we present the high-resolution solution structure and structural dynamics of the D' region of VWF, which constitutes the major FVIII binding site. D' consists of 2 domains, trypsin-inhibitor-like (TIL') and E', of which the TIL' domain lacks extensive secondary structure, is strikingly dynamic and harbors a cluster of pathological mutations leading to decreased FVIII binding affinity (type 2N von Willebrand disease [VWD]). This indicates that the backbone malleability of TIL' is important for its biological activity. The principal FVIII binding site is localized to a flexible, positively charged region on TIL', which is supported by the rigid scaffold of the TIL' and E' domain ß sheets. Furthermore, surface-charge mapping of the TIL'E' structure reveals a potential mechanism for the electrostatically guided, high-affinity VWF⋅FVIII interaction. Our findings provide novel insights into VWF⋅FVIII complex formation, leading to a greater understanding of the molecular basis of the bleeding diathesis type 2N VWD.

Phase II study to evaluate the safety and efficacy of intravenous palonosetron (PAL) in primary malignant glioma (MG) patients receiving standard radiotherapy (RT) and concomitant temozolomide (TMZ).

BACKGROUND: In malignant glioma (MG) patients undergoing radiation therapy (RT) with concomitant temozolomide, chemoradiation-induced nausea and vomiting (cRINV) degrades quality of life (QoL) and reduces treatment adherence, which thereby potentially compromises cancer control. METHODS: We conducted a 6-week phase II single-arm trial of PAL, a second-generation 5-HT3RA antiemetic, for cRINV prevention in MG patients receiving radiation therapy (RT; 54-60 Gy) and concomitant daily temozolomide (TMZ; 75 mg/m(2)/dX42d). Each week before radiation, patients received single-dose palonosetron (PAL) 0.25 mg IV (total = 6 doses). With safety/tolerability as the primary endpoint, the study was designed to differentiate between toxicity rates of 25 % (unacceptable) and 10 % (acceptable) toxicity rates. Secondary endpoints included the percentage of patients achieving cRINV complete response (CR: no emesis or rescue antiemetic) and QoL. Patients reported adverse effects in Common Toxicity Criteria for Adverse Events diaries; recorded vomiting, nausea, and rescue medication use in diaries (which were used to assess cRINV-CR); and reported QoL 4 days/week using the Modified Functional Living Index-Emesis (M-FLIE) and Osoba nausea and vomiting/retching modules. RESULTS: We enrolled 38 patients (mean age 59 years, 55 % female, 95 % white, 68 % used oral corticosteroids, 76 % reported low alcohol use). Four patients (10.5 %) experienced unacceptable treatment-related toxicity, defined as any grade 3, 4, or 5 non-hematologic toxicity. M-FLIE and Osoba scores showed no evidence of treatment impact on QoL. Overall, cRINV-CR rates for 6 weeks ranged from 67-79 %. CONCLUSION: Single-dose weekly PAL is a safe and tolerable antiemetic for cRINV prevention in MG patients receiving standard RT and concomitant TMZ.

Ligand-dependent dynamics of the active-site lid in bacterial dimethylarginine dimethylaminohydrolase.

The dimethylarginine dimethylaminohydrolase (DDAH) enzyme family has been the subject of substantial investigation as a potential therapeutic target for the regulation of vascular tension. DDAH enzymes catalyze the conversion of asymmetric N(η),N(η)-dimethylarginine (ADMA) to l-citrulline. Here the influence of substrate and product binding on the dynamic flexibility of DDAH from Pseudomonas aeruginosa (PaDDAH) has been assessed. A combination of heteronuclear NMR spectroscopy, static and time-resolved fluorescence measurements, and atomistic molecular dynamics simulations was employed. A monodisperse monomeric variant of the wild-type enzyme binds the reaction product l-citrulline with a low millimolar dissociation constant. A second variant, engineered to be catalytically inactive by substitution of the nucleophilic Cys249 residue with serine, can still convert the substrate ADMA to products very slowly. This PaDDAH variant also binds l-citrulline, but with a low micromolar dissociation constant. NMR and molecular dynamics simulations indicate that the active site "lid", formed by residues Gly17-Asp27, exhibits a high degree of internal motion on the picosecond-to-nanosecond time scale. This suggests that the lid is open in the apo state and allows substrate access to the active site that is otherwise buried. l-Citrulline binding to both protein variants is accompanied by an ordering of the lid. Modification of PaDDAH with a coumarin fluorescence reporter allowed measurement of the kinetic mechanism of the PaDDAH reaction. A combination of NMR and kinetic data shows that the catalytic turnover of the enzyme is not limited by release of the l-citrulline product. The potential to develop the coumarin-PaDDAH adduct as an l-citrulline sensor is discussed.

Stereotactic body radiotherapy: a critical review for nonradiation oncologists.

Stereotactic body radiotherapy (SBRT) involves the treatment of extracranial primary tumors or metastases with a few, high doses of ionizing radiation. In SBRT, tumor kill is maximized and dose to surrounding tissue is minimized, by precise and accurate delivery of multiple radiation beams to the target. This is particularly challenging, because extracranial lesions often move with respiration and are irregular in shape, requiring careful treatment planning and continual management of this motion and patient position during irradiation. This review presents the rationale, process workflow, and technology for the safe and effective administration of SBRT, as well as the indications, outcome, and limitations for this technique in the treatment of lung cancer, liver cancer, and metastatic disease.

Using ¹5N-ammonium to characterise and map potassium binding sites in proteins by NMR spectroscopy.

A variety of enzymes are activated by the binding of potassium ions. The potassium binding sites of these enzymes are very specific, but ammonium ions can often replace potassium ions in vitro because of their similar ionic radii. In these cases, ammonium can be used as a proxy for potassium to characterise potassium binding sites in enzymes: the (1) H,(15) N spin-pair of enzyme-bound (15) NH4 (+) can be probed by (15) N-edited heteronuclear NMR experiments. Here, we demonstrate the use of NMR spectroscopy to characterise binding of ammonium ions to two different enzymes: human histone deacetylase 8 (HDAC8), which is activated allosterically by potassium, and the bacterial Hsp70 homologue DnaK, for which potassium is an integral part of the active site. Ammonium activates both enzymes in a similar way to potassium, thus supporting this non-invasive approach. Furthermore, we present an approach to map the observed binding site onto the structure of HDAC8. Our method for mapping the binding site is general and does not require chemical shift assignment of the enzyme resonances.

MRI order appropriateness for chronic neck pain: Comparison of ordering practices and treatment outcomes for primary care physicians and specialists.

Chronic neck pain is a common reason for doctor visits in the United States. This diagnosis can be evaluated through patient history, physical examination, and judicious use of radiographs. However, possible inappropriate magnetic resonance imaging (MRI) ordering persists. We hypothesized that no difference in ordering practices, ordering appropriateness, and subsequent intervention would be appreciated regarding physician specialty, location, patient characteristics, and history and physical exam findings. A multisite retrospective review of cervical spine MRI between 2014 and 2018 was performed. A total of 332 patients were included. Statistical analysis was used to assess MRI order appropriateness, detail of history and physical exam findings, and intervention decision-making among different specialties. If significant differences were found, multiple linear regression was performed to evaluate the association of MRI order appropriateness regarding physician specialty, location, patient characteristics and history, and physical exam findings. The significance level for all tests was set at <0.05 Orthopedic surgeons ordered MRIs most appropriately with an average American College of Radiology (ACR) score of 8.4 (p < 0.005). Orthopedic surgeons had more comprehensive physical exams as compared to the remaining specialties. The decision for intervention did not vary by physician specialty or ACR score, except for patients of pain medicine physicians who received pain management (p = 0.000). Orthopedic surgeons utilize MRI most appropriately and have more comprehensive physical exams. These findings suggest a need for increased physician education on what indicates an appropriate MRI order to improve the use of resources and further protect patient risk-benefit profiles. Further research elucidating factors to minimize negative findings in "appropriate" MRIs is indicated. Clinical significance: More detailed physical exams may lead to more appropriately ordered MRIs, subsequently resulting in surgery or procedures being performed when appropriately indicated. This suggests the need for increased physician education on when MRI ordering is appropriate for chronic neck pain to improve the use of resources and further protect patient risk-benefit profiles.

Phosphopeptide binding to the N-SH2 domain of tyrosine phosphatase SHP2 correlates with the unzipping of its central ß-sheet.

SHP2 is a tyrosine phosphatase that plays a regulatory role in multiple intracellular signaling cascades and is known to be oncogenic in certain contexts. In the absence of effectors, SHP2 adopts an autoinhibited conformation with its N-SH2 domain blocking the active site. Given the key role of N-SH2 in regulating SHP2, this domain has been extensively studied, often by X-ray crystallography. Using a combination of structural analyses and molecular dynamics (MD) simulations we show that the crystallographic environment can significantly influence the structure of the isolated N-SH2 domain, resulting in misleading interpretations. As an orthogonal method to X-ray crystallography, we use a combination of NMR spectroscopy and MD simulations to accurately determine the conformation of apo N-SH2 in solution. In contrast to earlier reports based on crystallographic data, our results indicate that apo N-SH2 in solution primarily adopts a conformation with a fully zipped central ß-sheet, and that partial unzipping of this ß-sheet is promoted by binding of either phosphopeptides or even phosphate/sulfate ions.