A Strategy Based on Aggregation-Induced Ratiometric Emission to Differentiate Molecular Weight of Supramolecular Polymers

Molecular weight has an important bearing on the properties of supramolecular polymers. However, the intuitive differentiation of the molecular weight of supramolecular polymers remains challenging. Given this situation, establishing a reliable relationship between fluorescence properties and molecular weight may be a promising strategy. Herein, we prepared a supramolecular monomer M1 with aggregation-induced ratiometric emission characteristics. With the increasing M1 concentration (0.100-100 mM), the average degree of polymerization (DP_DOSY ) rose from 1.00 to 293. Meanwhile, the color changed from dark blue to cyan, finally to yellow-green in the same concentration range. Hence, the intuitive relationship between DP_DOSY and fluorescence colors was constructed, allowing the visual differentiation of molecular weight. Moreover, the fluorescence color could be regulated by introducing a competitive molecule to induce the depolymerization of supramolecular polymers.

Distribution of persistent free radicals in different molecular weight fractions from peat humic acids and their impact in reducing goethite

Humic substances, the most abundant component of soil organic matter, play vital roles in the biogeochemical cycles and pollutant redox reactions. However, the knowledge regarding the distribution of persistent free radicals (PFRs) and redox capacity in different molecular weight fractions (MWF) of humic acid (HA) and their impact on the transformation of iron oxide minerals remains unknown. In this study, we separated bulk HA into various MWF using dialysis methods and systematically investigated their PFRs properties, redox capacity, and the impact in reducing goethite. The results showed that the PFRs in the low MWF (<3500, <7000, and <14,000 Da) can be assigned to oxygen-centered organic radicals while those in the bulk and high MWF (14000-retentate) were assigned to carbon-centered organic radicals. The PFRs concentrations of low MWF were 0.20-0.45 × 10¹⁶ spins/g, far less than those of bulk HA (3.04 × 10¹⁶ spins/g) and 14000-retentate (1.30 × 10¹⁶ spins/g). The total concentrations of reactive oxygen species (ROS) induced by PFRs in HA fractions ranged from 8.04 × 10¹⁶ (in 14000-retentate) to 32.35 × 10¹⁶ spins/g (in bulk HA). Compared with the low MWF, the 14000-retentate fractions had the higher reducing capacity, which was positively related to the content of PFRs and phenolic hydroxyl in HA. The results obtained provide valuable insight into the geochemistry processes of Fe-containing minerals during their interaction with HA in the natural environment. Overall, the results obtained provide valuable insight into the geochemical behaviors of HA-associated PFRs under natural conditions.

Protein and glycan molecular weight determination of highly glycosylated HIV-1 envelope trimers by HPSEC-MALS

High Performance Size-Exclusion Chromatography coupled with Multi-Angle Light Scattering detection (HPSEC-MALS) is an important tool to provide a reliable molecular weight measurement for a large complex biomolecule. A recent HIV-1 soluble envelope trimer vaccine candidate, BG505 DS-SOSIP.664, is among the most glycosylated proteins to enter a clinical trial to date, and determination of its protein and glycan molecular weight is one of the key attributes in pre-clinical characterization. However, protein and glycans possess disparate dndcvalues making molecular weight measurement inaccurate in conventional SEC-MALS. To overcome these challenges, a simple mathematically guided experiment was explored, and a composite dndcvalue was established by utilizing protein and glycan mass contributions for the HIV-1 envelope trimer. This establishment was further verified by an orthogonal mass spectrometry analysis. This innovative, simple, and quick analytical approach can be applied broadly to measuring the molecular weight of various composite molecular structures, such as complex glycoconjugates.

Therapeutic Plasma Exchange Using Membrane Plasma Separation

Therapeutic plasma exchange is a blood purification technique designed for the removal of large molecular weight toxins such as pathogenic antibodies and lipoproteins. Plasma exchange can be performed either by membrane separation or centrifugation. Centrifugal plasma exchange is more common in the United States, while membrane separation is more popular in Germany and Japan. The membrane separation technique is similar to the ultrafiltration procedures performed with a standard dialysis machine but in which the membrane's pores are large enough to allow removal of all circulating molecules while retaining the cellular components. The current availability of plasma separation membranes compatible with CRRT systems has dramatically increased the potential for almost all nephrologists to perform these treatments. This review describes the membrane separation techniques available in the United States, the practical aspects of ordering and operating a membrane separation plasma exchange procedure, and its possible complications.

Variability of Two Metabolomic Platforms in CKD

BACKGROUND AND OBJECTIVES

Nontargeted metabolomics can measure thousands of low-molecular-weight biochemicals, but important gaps limit its utility for biomarker discovery in CKD. These include the need to characterize technical and intraperson analyte variation, to pool data across platforms, and to outline analyte relationships with eGFR.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Plasma samples from 49 individuals with CKD (eGFR<60 ml/min per 1.73 m² and/or ≥1 g proteinuria) were examined from two study visits; 20 samples were repeated as blind replicates. To enable comparison across two nontargeted platforms, samples were profiled at Metabolon and the Broad Institute.

RESULTS

The Metabolon platform reported 837 known metabolites and 483 unnamed compounds (selected from 44,953 unknown ion features). The Broad Institute platform reported 594 known metabolites and 26,106 unknown ion features. Median coefficients of variation (CVs) across blind replicates were 14.6% (Metabolon) and 6.3% (Broad Institute) for known metabolites, and 18.9% for (Metabolon) unnamed compounds and 24.5% for (Broad Institute) unknown ion features. Median CVs for day-to-day variability were 29.0% (Metabolon) and 24.9% (Broad Institute) for known metabolites, and 41.8% for (Metabolon) unnamed compounds and 40.9% for (Broad Institute) unknown ion features. A total of 381 known metabolites were shared across platforms (median correlation 0.89). Many metabolites were negatively correlated with eGFR at P<0.05, including 35.7% (Metabolon) and 18.9% (Broad Institute) of known metabolites.

CONCLUSIONS

Nontargeted metabolomics quantifies >1000 analytes with low technical CVs, and agreement for overlapping metabolites across two leading platforms is excellent. Many metabolites demonstrate substantial intraperson variation and correlation with eGFR.

Regulatory Considerations for Hemodiafiltration in the United States

Online hemodiafiltration provides greater removal of higher molecular weight uremic retention solutes than conventional high-flux hemodialysis. However, online hemodiafiltration is used sparsely in the United States in part because of a paucity of delivery systems cleared for clinical use by the US Food and Drug Administration. Although a pathway for regulatory approval exists in the United States, concerns remain, particularly regarding online production of the large volumes of sterile, nonpyrogenic substitution fluid infused directly into the bloodstream to maintain fluid balance. Clearly defined testing protocols, acceptable to Food and Drug Administration, will be useful to show that an online hemodiafiltration system is capable of routinely achieving a sterility assurance level of 10-6 and nonpyrogenic levels of endotoxin. Large-scale clinical experience has shown that systems providing this level of performance when combined with certain design features, such as redundancy, and an appropriate quality management process can routinely and safely produce substitution fluid for online hemodiafiltration.

Hemodiafiltration to Address Unmet Medical Needs ESKD Patients

Hemodiafiltration combines diffusive and convective solute removal in a single therapy by ultrafiltering 20% or more of the blood volume processed using a high-flux hemodialyzer and maintaining fluid balance by infusing sterile nonpyrogenic replacement fluid directly into the patient's blood. In online hemodiafiltration, the large volumes of replacement fluid required are obtained by online filtration of standard dialysate through a series of bacteria- and endotoxin-retaining filters. Currently available systems for online hemodiafiltration are on the basis of conventional dialysis machines with added features to safely prepare and infuse replacement fluid and closely control fluid balance. Hemodiafiltration provides greater removal of higher molecular weight uremic retention solutes than conventional high-flux hemodialysis, and recently completed randomized, controlled clinical trials suggest better patient survival with online hemodiafiltration compared with standard high-flux hemodialysis when a high convection volume is delivered. Hemodiafiltration is also associated with improvements in other clinical outcomes, such as a reduction in intradialytic hypotension, and it is now used routinely to treat >100,000 patients, mainly in Europe and Japan.

Effects of Molecular Weight and Concentration of Poly(Acrylic Acid) on Biomimetic Mineralization of Collagen

Inspired by nature, poly(acrylic acid) (PAA) and other polyelectrolytes have been used as noncollagenous proteins (NCPs) surrogates for biomimetic intrafibrillar mineralization of collagen fibrils and thus, to model the ultrastructure of bone, to study the mechanism of bone mineralization and, more scarcely to fabricate scaffolds for hard tissue engineering. The objective of this study was to systematically investigate the effect of the molecular weight (MW) and the concentration of PAA on the rate and pattern of biomineralization of collagen matrices. Densified type I collagen films were mineralized in supersaturated PAA-stabilized amorphous calcium-phosphate (PAA-ACP) solutions containing increasing MW (2 kDa, 50 kDA, 450 kDa) and concentrations (10, 25, 50 mg/L) of PAA up to 7 days. The stability and physical properties of collagen-free PAA-ACP solutions were also investigated. In our system, lowering PAA MW and increasing PAA concentration resulted in solutions with increasing stability. Over stable PAA-ACP solutions that fully inhibited mineralization of the collagen matrices were achieved using PAA 2k-50. Conversely, unstable solutions were obtained using high PAA MW at low concentrations. Nucleation and growth of significant amount of extrafibrillar minerals on the collagen fibrils was obtained using these solutions. In a wide range of combined MW and concentration of PAA we obtained intrafibrillar mineralization of collagen with hydroxyapatite crystals aligned parallel to the collagen fibril as in natural tissues. Intrafibrillar mineralization was correlated with PAA-ACP stability and growth of the PAA-ACP particles in solution. Our results support using PAA to surrogate NCPs function as selective inhibitors or promoters of biological mineralization and provide parameters to manufacture new biomimetic scaffolds and constructs for bone and dentin tissue engineering.

Exploring the Clinical Relevance of Providing Increased Removal of Large Middle Molecules

Dialysis technologies have continued to advance over recent decades; however, these advancements have not always been met with improved patient outcomes. In part, the high morbidity and mortality associated with dialysis have been attributed to a group of uremic toxins, which are described as "difficult to remove." With a new generation of hemodialysis membranes now making meaningful clearance of these molecules possible, it is an apt time to review the clinical relevance of these middle molecules. Our review describes the developments in membrane technology that enable the removal of large middle molecules (molecular mass >15 kD) that is limited with high-flux dialysis membranes. Of the known 58 middle molecules, a literature search identified 27 that have molecular mass >15 kD. This group contains cytokines, adipokines, hormones, and other proteins. These molecules are implicated in chronic inflammation, atherosclerosis, structural heart disease, and secondary immunodeficiency in the literature. Single-center safety and efficacy studies have identified that use of these membranes in maintenance dialysis populations is associated with limited loss of albumin and increased clearance of large middle molecules. Larger, robustly conducted, multicenter studies are now evaluating these findings. After completion of these safety and efficacy studies, the perceived clinical benefits of providing clearance of large middle molecules must be assessed in rigorously conducted, randomized clinical studies.

Glomerular Pathology in Dent Disease and Its Association with Kidney Function

BACKGROUND AND OBJECTIVES

Dent disease is a rare X-linked disorder characterized by low molecular weight proteinuria and often considered a renal tubular disease. However, glomerulosclerosis was recently reported in several patients. Thus, Dent disease renal histopathologic features were characterized and assessed, and their association with kidney function was assessed.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Clinical renal pathology reports and slides (where available) were collected from 30 boys and men in eight countries who had undergone clinical renal biopsy between 1995 and 2014.

RESULTS

Median (25th, 75th percentiles) age at biopsy was 7.5 (5, 19) years with an eGFR of 69 (44, 94) ml/min per 1.73 m2 and a 24-hour urine protein of 2000 (1325, 2936) mg. A repeat biopsy for steroid-resistant proteinuria was performed in 13% (four of 30) of the patients. Prominent histologic findings included focal global glomerulosclerosis in 83% (25 of 30; affecting 16%±19% glomeruli), mild segmental foot process effacement in 57% (13 of 23), focal interstitial fibrosis in 60% (18 of 30), interstitial lymphocytic infiltration in 53% (16 of 30), and tubular damage in 70% (21 of 30). Higher percentages of globally sclerotic glomeruli, foot process effacement, and interstitial inflammation were associated with lower eGFR at biopsy, whereas foot process effacement was associated with steeper annual eGFR decline.

CONCLUSIONS

These associations suggest a potential role for glomerular pathology, specifically involving the podocyte, in disease progression, which deserves further study. Furthermore, Dent disease should be suspected in boys and men who have unexplained proteinuria with focal global glomerulosclerosis and segmental foot process effacement on renal biopsy.

Paraprotein-Related Kidney Disease: Evaluation and Treatment of Myeloma Cast Nephropathy

Nearly 50% of patients with multiple myeloma develop renal disease, most commonly from AKI caused by cast nephropathy. Development of AKI is associated with poor 1-year survival and reduces the therapeutic options available to patients. There is a great need for more effective therapies. Cast nephropathy is caused by the interaction and aggregation of filtered free light chains and Tamm-Horsfall protein causing intratubular obstruction and damage. The key to treating cast nephropathy is rapid lowering of free light chains, because this correlates with renal recovery. Newer chemotherapy agents rapidly lower free light chains and have been referred to as renoprotective. There is additional great interest in using extracorporeal therapies to remove serum free light chains. Small trials initially showed benefit of therapeutic plasma exchange to improve renal outcomes in cast nephropathy, but a large randomized trial of therapeutic plasma exchange failed to show benefit. A newer technique is extended high-cutoff hemodialysis. This modality uses a high molecular weight cutoff filter to remove free light chains. To date, trials of high-cutoff hemodialysis use in patients with cast nephropathy have been encouraging. However, there are no randomized trials showing the benefit of high-cutoff hemodialysis when used in addition to newer chemotherapeutic regimens. Until these studies are available, high-cutoff hemodialysis cannot be recommended as standard of care.

Molecular Weight, Protein Binding Affinity and Methane Mitigation of Condensed Tannins from Mangosteen-peel (Garcinia mangostana L)

The objectives of this study were to determine the molecular weight of condensed tannins (CT) extracted from mangosteen (Garcinia mangostana L) peel, its protein binding affinity and effects on fermentation parameters including total gas, methane (CH₄) and volatile fatty acids (VFA) production. The average molecular weight (M_w) of the purified CT was 2,081 Da with a protein binding affinity of 0.69 (the amount needed to bind half the maximum bovine serum albumin). In vitro gas production declined by 0.409, 0.121, and 0.311, respectively, while CH₄ production decreased by 0.211, 0.353, and 0.549, respectively, with addition of 10, 20, and 30 mg CT/500 mg dry matter (DM) compared to the control (p<0.05). The effects of CT from mangosteen-peel on in vitro DM degradability (IVDMD) and in vitro N degradability was negative and linear (p<0.01). Total VFA, concentrations of acetic, propionic, butyric and isovaleric acids decreased linearly with increasing amount of CT. The aforementioned results show that protein binding affinity of CT from mangosteen-peel is lower than those reported for Leucaena forages, however, the former has stronger negative effect on IVDMD. Therefore, the use of mangosteen-peel as protein source and CH₄ mitigating agent in ruminant feed requires further investigations.