Water Plays Key Roles in Stabilities of Wild Type and Mutant Transthyretin Complexes.

Transthyretin (TTR), a 56 kDa homotetramer that is involved in the transport of thyroxine and retinol, has been linked to amyloidosis through disassembly of tetramers to form monomers, dimers, and trimers that then reassemble into higher order oligomers and/or fibrils. Hybrid TTR (hTTR) tetramers are found in heterozygous individuals that express both wild type TTR (wt-TTR) and mutant TTR (mTTR) forms of the protein, and these states display increased rates of amyloidosis. Here we monitor subunit exchange (SUE) reactions involving homomeric and mixed tetramers using high resolution native mass spectrometry (nMS). Our results show evidence that differences in TTR primary structure alter tetramer stabilities, and hTTR products can form spontaneously by SUE reactions. In addition, we find that solution temperature has strong effects on TTR tetramer stabilities and formation of SUE products. Lower temperatures promote formation of hTTR tetramers containing L55P and V30M subunits, whereas small effects on the formation of hTTR tetramers containing F87A and T119M subunits are observed. We hypothesize that the observed temperature dependent stabilities and subsequent SUE behavior are a result of perturbations to the network of "two kinds of water": hydrating and structure stabilizing water molecules (Spyrakis et al. J. Med. Chem. 2017, 60 (16), 6781-6827; Xu et al. Soft Matter 2012, 8, 324-336) that stabilize wt-TTR and mTTR tetramers. The results presented in this work illustrate the utility of high resolution nMS for studies of the structures, stabilities, and dynamics of protein complexes that directly influence SUE reactions.

Production, isolation, and shipment of clinically relevant quantities of astatine-211: A simple and efficient approach to increasing supply.

The alpha emitter astatine-211 (211At) is a promising candidate for cancer treatment based on Targeted Alpha (α) Therapy (TAT). A small number of facilities, distributed across the United States, are capable of accelerating α-particle beams to produce 211At. However, challenges remain regarding strategic methods for shipping 211At in a form adaptable to advanced radiochemistry reactions and other uses of the radioisotope. PURPOSE: Our method allows shipment of 211At in various quantities in a form convenient for further radiochemistry. PROCEDURES: For this study, a 3-octanone impregnated Amberchrom CG300M resin bed in a column cartridge was used to separate 211At from the bismuth matrix on site at the production accelerator (Texas A&M) in preparation for shipping. Aliquots of 6 M HNO3 containing up to ≈2.22 GBq of 211At from the dissolved target were successfully loaded and retained on columns. Exempt packages (<370 MBq) were shipped to a destination radiochemistry facility, University of Texas MD Anderson Cancer Center, in the form of a convenient air-dried column. Type A packages have been shipped overnight to University of Alabama at Birmingham. MAIN FINDINGS: Air-dried column hold times of various lengths did not inhibit simple and efficient recovery of 211At. Solution eluted from the column was sufficiently high in specific activity to successfully radiolabel a model compound, 4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)aniline (1), with 211At. The method to prepare and ship 211At described in this manuscript has also been used to ship larger quantities of 211At a greater distance to University of Alabama at Birmingham. PRINCIPAL CONCLUSIONS: The successful proof of this method paves the way for the distribution of 211At from Texas A&M University to research institutions and clinical oncology centers in Texas and elsewhere. Use of this simple method at other facilities has the potential increase the overall availability of 211At for preclinical and clinical studies.

Presurgery resting-state local graph-theory measures predict neurocognitive outcomes after brain surgery in temporal lobe epilepsy.

OBJECTIVE: This study determined the ability of resting-state functional connectivity (rsFC) graph-theory measures to predict neurocognitive status postsurgery in patients with temporal lobe epilepsy (TLE) who underwent anterior temporal lobectomy (ATL). METHODS: A presurgical resting-state functional magnetic resonance imaging (fMRI) condition was collected in 16 left and 16 right TLE patients who underwent ATL. In addition, patients received neuropsychological testing pre- and postsurgery in verbal and nonverbal episodic memory, language, working memory, and attention domains. Regarding the functional data, we investigated three graph-theory properties (local efficiency, distance, and participation), measuring segregation, integration and centrality, respectively. These measures were only computed in regions of functional relevance to the ictal pathology, or the cognitive domain. Linear regression analyses were computed to predict the change in each neurocognitive domain. RESULTS: Our analyses revealed that cognitive outcome was successfully predicted with at least 68% of the variance explained in each model, for both TLE groups. The only model not significantly predictive involved nonverbal episodic memory outcome in right TLE. Measures involving the healthy hippocampus were the most common among the predictors, suggesting that enhanced integration of this structure with the rest of the brain may improve cognitive outcomes. Regardless of TLE group, left inferior frontal regions were the best predictors of language outcome. Working memory outcome was predicted mostly by right-sided regions, in both groups. Overall, the results indicated our integration measure was the most predictive of neurocognitive outcome. In contrast, our segregation measure was the least predictive. SIGNIFICANCE: This study provides evidence that presurgery rsFC measures may help determine neurocognitive outcomes following ATL. The results have implications for refining our understanding of compensatory reorganization and predicting cognitive outcome after ATL. The results are encouraging with regard to the clinical relevance of using graph-theory measures in presurgical algorithms in the setting of TLE.