Amyloid-ß Tetramers and Divalent Cations at the Membrane/Water Interface: Simple Models Support a Functional Role.

Charge polarization at the membrane interface is a fundamental process in biology. Despite the lower concentration compared to the abundant monovalent ions, the relative abundance of divalent cations (Ca2+, Mg2+, Zn2+, Fe2+, Cu2+) in particular spaces, such as the neuron synapse, raised many questions on the possible effects of free multivalent ions and of the required protection of membranes by the eventual defects caused by the free forms of the cations. In this work, we first applied a recent realistic model of divalent cations to a well-investigated model of a polar lipid bilayer, di-myristoyl phosphatidyl choline (DMPC). The full atomistic model allows a fairly good description of changes in the hydration of charged and polar groups upon the association of cations to lipid atoms. The lipid-bound configurations were analyzed in detail. In parallel, amyloid-ß 1-42 (Aß42) peptides assembled into tetramers were modeled at the surface of the same bilayer. Two of the protein tetramers' models were loaded with four Cu2+ ions, the latter bound as in DMPC-free Aß42 oligomers. The two Cu-bound models differ in the binding topology: one with each Cu ion binding each of the monomers in the tetramer; one with pairs of Cu ions linking two monomers into dimers, forming tetramers as dimers of dimers. The models here described provide hints on the possible role of Cu ions in synaptic plasticity and of Aß42 oligomers in storing the same ions away from lipids. The release of structurally disordered peptides in the synapse can be a mechanism to recover ion homeostasis and lipid membranes from changes in the divalent cation concentration.

Commentary on: Divalent metal cofactors differentially modulate RadA-mediated strand invasion and exchange in Saccharolobus solfataricus.

RecA ATPases are a family of proteins that catalyzes the exchange of complementary DNA regions via homologous recombination. They are conserved from bacteria to humans and are crucial for DNA damage repair and genetic diversity. In this work, Knadler et al. examine how ATP hydrolysis and divalent cations impact the recombinase activity of Saccharolobus solfataricus RadA protein (ssoRadA). They find that the ssoRadA-mediated strand exchange depends on ATPase activity. The presence of Manganese reduces ATPase activity and enhances strand exchange, while calcium inhibits ATPase activity by preventing ATP binding to the protein, yet destabilizes the nucleoprotein ssoRadA filaments, allowing strand exchange regardless of the ATPase activity. Although RecA ATPases are highly conserved, this research offers intriguing new evidence that each member of the family requires individual evaluation.

Effect of divalent cations on electrochemiluminescence of metal-organic frameworks in bioassay.

The structural characteristics of electrochemiluminescent (ECL) microreticula enabled flexible designs for probing specific molecules. However, bioanalysts paid little attention to the impact of concomitant electrolytic carriers on ECL responsiveness of these grids. Our previous finding confirmed the collisional quenching of ECL radiative secondary building units from polarized Br- and I-. To further address this concern, herein typical cationic commonplaces including Na+, K+, Ca2+, … in buffer plus regular transition metals - their influences upon the ECL performance of a well-defined zinc porphyrin-organic framework (ZnPOF) were inspected in a one-by-one manner. Except for Na+/K+, a dozen of divalent metal chlorides exerted an adverse effect in the form of Stern-Volmer quenching on the ECL brightness, which was illuminated to be cation channeling in open voids of ZnPOFs and bonding with O2-reactive sites as exemplified by the model Ca2+ via systematic compositional investigation. Following this principle, a simplistic Ca2+-sensitive sensor was developed for quantitative evaluation of health-care calcium supplements with high precision. Above all, this work highlighted the non-negligible interference from those Mn + requisites to the susceptible MOF-based ECL, which should be paid extra attention in bioassays and mechanistic analyses.

Usnic Acid-Mediated Exchange of Protons for Divalent Metal Cations across Lipid Membranes: Relevance to Mitochondrial Uncoupling.

Usnic acid (UA), a unique lichen metabolite, is a protonophoric uncoupler of oxidative phosphorylation, widely known as a weight-loss dietary supplement. In contrast to conventional proton-shuttling mitochondrial uncouplers, UA was found to carry protons across lipid membranes via the induction of an electrogenic proton exchange for calcium or magnesium cations. Here, we evaluated the ability of various divalent metal cations to stimulate a proton transport through both planar and vesicular bilayer lipid membranes by measuring the transmembrane electrical current and fluorescence-detected pH gradient dissipation in pyranine-loaded liposomes, respectively. Thus, we obtained the following selectivity series of calcium, magnesium, zinc, manganese and copper cations: Zn2+ > Mn2+ > Mg2+ > Ca2+ >> Cu2+. Remarkably, Cu2+ appeared to suppress the UA-mediated proton transport in both lipid membrane systems. The data on the divalent metal cation/proton exchange were supported by circular dichroism spectroscopy of UA in the presence of the corresponding cations.

Effects of colloids on ammonia nitrogen release under different ion conditions in natural sediments of Lake Taihu, China.

Colloids act as vectors for accelerating contaminant movement in natural porous media such as lake sediments. Releasing characteristics of colloids and colloid-adsorbed ammonia nitrogen from lake sediments with the presence of monovalent and divalent cations were studied by an indoor anaerobic flooding incubation experiment. Results show that release of colloids was influenced by valence state and strength of the cation. In the presence of Na+ and Ca2+, the concentrations of the colloids in the overlying water were 11-163 mg/L and 13-88 mg/L during the entire incubation process and their values increased by 12.7%-122.3% and 1.5%-29.1%, respectively, compared to the control group, which indicated that the promoting effect of monovalent cations on release of colloids was more obvious than that of divalent cations. However, the total mass of colloids release reduced with the increasing ionic strength. Colloid-adsorbed ammonia nitrogen in the overlying water reached 0.15-1.72 mg/L and 0.15-1.12 mg/L with the presence of Na+ and Ca2+ and was higher 61.7%-161.7% and 21.3%-80.9%, respectively, than in the control group, indicating a consequent effect of ion conditions on the release of ammonium nitrogen from sediments. A significant positive correlation between colloids and ammonia nitrogen concentration further shows that colloidal activity determinately resulted in the increase or decrease in the ammonia nitrogen concentration in the overlying water, which could adsorb ammonia nitrogen and act as vehicles to carry ammonia nitrogen together into the aqueous medium or sink into the sediment. The release of ammonia nitrogen is possibly enhanced by colloidal behavior and varies with spatiotemporal ionic conditions in natural sediments. These findings are essential for improving the understanding of the geological fate of environmental colloids and associated nutritive salts, which provide scientific basis and technical support for the control of endogenous pollution and the comprehensive treatment of water bodies in Lake Taihu.

Effect of Ferrous Ion on Heat-Induced Aroma Deterioration of Green Tea Infusion.

Aroma deterioration is one of the biggest problems in processing tea beverages. The aroma of tea infusion deteriorates fast during heat sterilization and the presence of ferrous ion (Fe2+) aggravates it. The underlying mechanism remains unveiled. In this study, Fe2+ was verified to deteriorate the aroma quality of green tea infusion with heat treatment. Catechins were necessary for Fe2+-mediated aroma deterioration. By enhancing the degradation of catechins, Fe2+ dramatically increased the production of hydrogen peroxide (H2O2). Fe2+ and H2O2 together exacerbated the aroma of green tea infusion with heat treatment. GC-MS analysis revealed that the presence of Fe2+ enhanced the loss of green/grassy volatiles and promoted the formation of new volatiles with diversified aroma characteristics, resulting in a dull scent of green tea infusion. Our results revealed how Fe2+ induced aroma deterioration of green tea infusion with heat treatment and could help guide tea producers in attenuating the aroma deterioration of tea infusion during processing.

Switching ON of Transcription-Translation System Using GUV Fusion by Co-supplementation of Calcium with Long-Chain Polyethylene Glycol.

Giant unilamellar vesicles (GUVs) have been used as a material for bottom-up synthetic biology. However, due to the semi-permeability of the membrane, the need for methods to fuse GUVs has increased. To this aim, methods that are simple and show low leakage during fusion are important. In this study, we report a method of GUV fusion by a divalent cation (Ca2+ ) enhanced with a long chain polyethylene glycol (PEG20k). The methods showed significant GUV fusion without leakage of internal components of GUVs and maintained cell-free transcription-translation ability inside the GUVs without external supplementation of macromolecules. We demonstrate that the Ca-PEG method can be applied for switching ON of transcription-translation in GUVs in a fusion-dependent manner. The method developed here can be applied to extend bottom-up synthetic biology and molecular robotics that use GUVs as a chassis.

From Secretion in Pichia pastoris to Application in Apple Juice Processing: Exo-Polygalacturonase from Sporothrix schenckii 1099-18.

BACKGROUND: Polygalacturonases are a group of enzymes under pectinolytic enzymes related to enzymes that hydrolyse pectic substances. Polygalacturonases have been used in various industrial applications such as fruit juice clarification, retting of plant fibers, wastewater treatment drinks fermentation, and oil extraction. OBJECTIVES: The study was evaluated at the heterologous expression, purification, biochemical characterization, computational modeling, and performance in apple juice clarification of a new exo-polygalacturonase from Sporothrix schenckii 1099-18 (SsExo-PG) in Pichia pastoris. METHODS: Recombinant DNA technology was used in this study. Two different pPIC9K plasmids were constructed with native signal sequence-ssexo-pg and alpha signal sequence-ssexo-pg separately. Protein expression and purification performed after plasmids transformed into the Pichia pastoris. Biochemical and structural analyses were performed by using pure SsExo-PG. RESULTS: The purification of SsExo-PG was achieved using a Ni-NTA chromatography system. The enzyme was found to have a molecular mass of approximately 52 kDa. SsExo-PG presented as stable at a wide range of temperature and pH values, and to be more storage stable than other commercial pectinolytic enzyme mixtures. Structural analysis revealed that the catalytic residues of SsExo- PG are somewhat similar to other Exo-PGs. The KM and kcat values for the degradation of polygalacturonic acid (PGA) by the purified enzyme were found to be 0.5868 µM and 179 s-1, respectively. Cu2+ was found to enhance SsExo-PG activity while Ag2+ and Fe2+ almost completely inhibited enzyme activity. The enzyme reduced turbidity up to 80% thus enhanced the clarification of apple juice. SsExo-PG showed promising performance when compared with other commercial pectinolytic enzyme mixtures. CONCLUSION: The clarification potential of SsExo-PG was revealed by comparing it with commercial pectinolytic enzymes. The following parameters of the process of apple juice clarification processes showed that SsExo-PG is highly stable and has a novel performance.

The interplay between a GC-rich oligonucleotide and copper ions on prion protein conformational and phase transitions.

The prion protein (PrP) misfolding to its infectious form is critical to the development of prion diseases, whereby various ligands are suggested to participate, such as copper and nucleic acids (NA). The PrP globular domain was shown to undergo NA-driven liquid-liquid phase separation (LLPS); this latter may precede pathological aggregation. Since Cu(II) is a physiological ligand of PrP, we argue whether it modulates phase separation altogether with nucleic acids. Using recombinant PrP, we investigate the effects of Cu(II) (at 6 M equivalents) and a previously described PrP-binding GC-rich DNA (equimolarly to protein) on PrP conformation, oligomerization, and phase transitions using a range of biophysical techniques. Raman spectroscopy data reveals the formation of the ternary complex. Microscopy suggests that phase separation is mainly driven by DNA, whereas Cu(II) has no influence. Our results show that DNA can be an adjuvant, leading to the structural conversion of PrP, even in the presence of an endogenous ligand, copper. These results provide new insights into the role of Cu(II) and NA on the phase separation, structural conversion, and aggregation of PrP, which are critical events leading to neurodegeneration.

Hypozincemia in COVID-19 Patients Correlates With Stronger Antibody Response.

Zinc ion as an enzyme cofactor exhibits antiviral and anti-inflammatory activity during infection, but circulating zinc ion level during Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infection is unclear. This study aimed to evaluate serum zinc ion level in Coronavirus Disease 2019 (COVID-19) patients and healthy subjects, as well as its correlation with antibodies against SARS-CoV-2. 114 COVID-19 patients and 48 healthy subjects (38 healthy volunteers and 10 close contacts of patients with COVID-19) were included. Zinc ion concentration and levels of antibodies against SARS-CoV-2 Spike 1 + Spike 2 proteins, nucleocapsid protein, and receptor-binding domain in serum were measured. Results showed that the concentration of zinc ion in serum from COVID-19 patients [median: 6.4 nmol/mL (IQR 1.5 - 12.0 nmol/mL)] were significantly lower than that from the healthy subjects [median: 15.0 nmol/mL (IQR 11.9 - 18.8 nmol/mL)] (p < 0.001) and the difference remained significant after age stratification (p < 0.001) or when the patients were at the recovery stage (p < 0.001). Furthermore, COVID-19 patients with more severe hypozincemia showed higher levels of IgG against the receptor-binding domain of SARS-CoV-2 spike protein. Further studies to confirm the effect of zinc supplementation on improving the outcomes of COVID-19, including antibody response against SARS-CoV-2, are warranted.

A colorimetric aptamer-based method for detection of cadmium using the enhanced peroxidase-like activity of Au-MoS2 nanocomposites.

In this work, a colorimetric aptamer-based method for detection of cadmium using gold nanoparticles modified MoS2 nanocomposites as enzyme mimic is established. In short, biotinylated Cd2+ aptamers are immobilized by biotin-avidin binding on the bottoms of the microplate, the complementary strands of Cd2+ aptamers are connected to the Au-MoS2 nanocomposites which have the function of enhanced peroxidase-like activity. The csDNA-Au-MoS2 signal probe and target Cd2+ compete for binding Cd2+ aptamer, the color change can be observed by addition of chromogenic substrate, thereby realizing visual detection of Cd2+. The absorbance of the solution at 450 nm has a clear linear relationship with the Cd2+ concentration. The linear range is 1-500 ng/mL, and the limit of detection is 0.7 ng/mL. The assay was used to test white wine samples, the results are consistent with those of atomic absorption spectrometry; which prove that this method can be used for detection of Cd2+ in real samples.

Phosphonium-ammonium-based di-cationic ionic liquids as antibacterial over the ESKAPE group.

Emergence of antibioresistance is currently a major threat of public health worldwide. Hence there is an urge need of finding new antibacterial material. Herein, we report a simple and eco-friendly method to synthesize homo and heterodicationic ionic liquids based on quaternary phosphonium and ammonium salt. In order to investigate the structure activity relationship (SAR) we measured the MICs of a series of 16 derivatives with structural variations (nature of cations and counter-ions, size of linker and alkyl side chains as well as structural symmetry) over a range of Gram-positive and Gram-negative bacterial strains from the ESKAPE group. Some of the tested structures exhibit high antimicrobial activities (MIC = 0.5 mg/L) and are active over a wide range of bacteria from Gram-positive to Gram-negative. Overall, these results reveal the strong potential of di-cationic derivatives as antibacterial agents and the determination of activities from structural features gives decisive information for future synthesis of such di-cationic structures for biocidal purpose.

Methacrylated gellan gum and hyaluronic acid hydrogel blends for image-guided neurointerventions.

Cell-based therapies delivered via intrathecal injection are considered as one of the most promising solutions for the treatment of amyotrophic lateral sclerosis (ALS). Herein, injectable manganese-based biocompatible hydrogel blends were developed, that can allow image-guided cell delivery. The hydrogels can also provide physical support for cells during injection, and at the intrathecal space after transplantation, while assuring cell survival. In this regard, different formulations of methacrylated gellan gum/hyaluronic acid hydrogel blends (GG-MA/HA) were considered as a vehicle for cell delivery. The hydrogels blends were supplemented with paramagnetic Mn2+ to allow a real-time monitorization of hydrogel deposition via T1-weighted magnetic resonance imaging (MRI). The developed hydrogels were easily extruded and formed a stable fiber upon injection into the cerebrospinal fluid. Hydrogels prepared with a 75 : 25 GG-MA to HA ratio supplemented with MnCl2 at 0.1 mM showed controlled hydrogel degradation, suitable permeability, and a distinct MRI signal in vitro and in vivo. Additionally, human-derived adipose stem cells encapsulated in 75 : 25 GG-MA/HA hydrogels remained viable for up to 14 days of culture in vitro. Therefore, the engineered hydrogels can be an excellent tool for injectable image-guided cell delivery approaches.

Chitosan/thiol functionalized metal-organic framework composite for the simultaneous determination of lead and cadmium ions in food samples.

In this work, a facile solid phase extraction (SPE) method was developed for the analysis of trace Pb2+ and Cd2+ by using chitosan/thiol modified metal-organic frameworks (CS/MOF-SH) composite as adsorbent followed by graphite furnace atomic absorption spectrometer (GF-AAS) detection. The potential influencing factors, such as solution pH, adsorbent dosage, and extraction time, were fully estimated. Under the optimized extraction conditions, the detection limits of Pb2+ and Cd2+ were 0.033 µg L-1 and 0.008 µg L-1, respectively. Compared to other studies, CS/MOF-SH not only possessed superior adsorption performance, but also had the advantages of ease of handling and recyclability. Encouragingly, the developed method was of high accuracy and could monitor trace Pb2+ and Cd2+ in various certified reference materials (rice, wheat and tea) with complicated matrices, demonstrating its practical potential for regular monitoring of trace heavy metal ions in real food samples.

Role of Divalent Cations in HIV-1 Replication and Pathogenicity.

Divalent cations are essential for life and are fundamentally important coordinators of cellular metabolism, cell growth, host-pathogen interactions, and cell death. Specifically, for human immunodeficiency virus type-1 (HIV-1), divalent cations are required for interactions between viral and host factors that govern HIV-1 replication and pathogenicity. Homeostatic regulation of divalent cations' levels and actions appear to change as HIV-1 infection progresses and as changes occur between HIV-1 and the host. In people living with HIV-1, dietary supplementation with divalent cations may increase HIV-1 replication, whereas cation chelation may suppress HIV-1 replication and decrease disease progression. Here, we review literature on the roles of zinc (Zn2+), iron (Fe2+), manganese (Mn2+), magnesium (Mg2+), selenium (Se2+), and copper (Cu2+) in HIV-1 replication and pathogenicity, as well as evidence that divalent cation levels and actions may be targeted therapeutically in people living with HIV-1.

Copper Complexing Capacity and Trace Metal Content in Common and Balsamic Vinegars: Impact of Organic Matter.

Complex formation is among the mechanisms affecting metal bioaccessibility. Hence, the quantification of organic metal complexation in food items is of interest. Organic ligands in solutions of environmental and/or food origin function as buffering agents against small changes in dissolved metal concentrations, being able to maintain free metal ion concentrations below the toxicity threshold. Organic matter in vinegars consists of bioactive compounds, such as polyphenols, Maillard reaction endproducts, etc., capable of complexing metal ions. Furthermore, transition metal ions are considered as micronutrients essential for living organisms exerting a crucial role in metabolic processes. In this study, differential pulse anodic stripping voltammetry (DPASV), a sensitive electrochemical technique considered to be a powerful tool for the study of metal speciation, was applied for the first time in vinegar samples. The concentrations of Cu complexing ligands (LT) in 43 vinegars retailed in Greece varied between 0.05 and 52 µM, with the highest median concentration determined in balsamic vinegars (14 µM), compared to that of common vinegars (0.86 µM). In 21% of the vinegar samples examined, LT values were exceeded by the corresponding total Cu concentrations, indicating the presence of free Cu ion and/or bound within labile inorganic/organic complexes. Red grape balsamic vinegars exhibited the highest density of Cu ligands per mass unit of organic matter compared to other foodstuffs such as herbal infusions, coffee brews, and beers. Among the 16 metals determined in vinegars, Pb is of particular importance from a toxicological point of view, whereas further investigation is required regarding potential Rb biomagnification.

Qualitative and quantitative 1 H NMR spectroscopy for determination of divalent metal cation concentration in model salt solutions, food supplements, and pharmaceutical products by using EDTA as chelating agent.

This paper introduces an 1 H NMR method to identify individual divalent metal cations Be2+ , Mg2+ , Ca2+ , Sr2+ , Zn2+ , Cd2+ , Hg2+ , Sn2+ , and Pb2+ in aqueous salt solutions through their unique signal shift and coupling after complexation with the salt of ethylenediaminetetraacetic acid (EDTA). Furthermore, quantitative determination applied for the divalent metal cations Ca2+ , Mg2+ , Hg2+ , Sn2+ , Pb2+ , and Zn2+ (limit of quantification: 5-22 µg/ml) can be achieved using an excess of EDTA with aqueous model salt solutions. An internal standard is not required because a known excess of EDTA is added and the remaining free EDTA can be used to recalculate the quantity of chelated metal cations. The utility of the method is demonstrated for the analysis of divalent cations in some food supplements and in pharmaceutical products.

Antifungal Activity of Lactic Acid Bacteria Isolates and Their Associations: The Effects of Ca and Mg Divalent Cations.

The study of effects of Ca2+ and Mg2+ on antifungal activity of lactic acid bacteria (LAB) isolates and their associations revealed inducing and inhibiting effects on antifungal activity. The addition of Ca2+ essentially inhibited the antifungal effect of L. rhamnosus MDC9661 but stimulated the activity of RIN-2003-Ls, MDC9632 and MDC9633 strains, as well as their associations. Mg2+ partly increased the inhibitory activity of LAB isolates, while the addition of ions combination did not cause changes of their antifungal activity. The supplementation of Ca2+ stimulated the antifungal effect of most associations against Penicillium sp., Trichoderma viride, Geotrichum candidum, and Aspergillus flavus compared with the native conditions. The addition of Mg2+ induced the antifungal activity of RIN-2003-Ls, MDC9632, MDC9633, and INR-2010-Tsov-G-St combinations. The antifungal effects of most associations were increased in the presence of ions mixture. The natural LAB associations including VKPM B-3386, MDC9632, and MDC9633 could not suppress the growth of any tested mold; however, the supplementation of ions combination revealed their antifungal effect against all kinds of molds. The finding of substantial stimulation of the most LAB associations antifungal effect by metal ions can be basis for creation of new effective antifungal preparations by the supplementation of ions combined mixture.

The effect of monovalent (Na+, K+) and divalent (Ca2+, Mg2+) cations on rapeseed oleosome (oil body) extraction and stability at pH 7.

Oleosomes are storage vehicles of TAGs in plant seeds. They are protected with a phospholipid-protein monolayer and extracted with alkaline aqueous media; however, pH adjustment intensifies the extraction process. Therefore, the aim of this work was to investigate the extraction mechanism of rapeseed oleosomes at pH 7 and at the presence of monovalent and divalent cations (Na+, K+, Mg2+, and Ca+2). The oleosome yield at pH 9.5 was 64 wt%, while the yield at pH 7 with H2O was just 43 wt.%. The presence of cations at pH 7, significantly enhanced the yield, with K+ giving the highest yield (64 wt.%). The cations affected the oleosome interface and their interactions. The presence of monovalent cations resulted in aggregation and minor coalescence, while divalent cations resulted in extensive coalescence. These results help to understand the interactions of oleosomes in their native matrix and design simple extraction processes at neutral conditions.

The effect of divalent cation complexation on anaerobically digested enhanced biological phosphorus removal sludge dewatering performance.

The effect of mono- and divalent cation concentrations on digested sludge dewatering characteristics was investigated in a full-scale study at the Harrisonburg-Rockingham Regional Sewer Authority, VA (HRRSA) and at an additional POTW (POTW B). At HRRSA, anaerobic digesters were fed with primary sludge, enhanced biological phosphorus removal (EBPR) WAS, and trucked-in DAF solids from a poultry processing facility, and digested sludge was dewatered by belt filter press. The POTW B digesters received EBPR WAS and primary sludge, and dewatering was by centrifuge. Visual MINTEQ 3.1 (Gustafsson, 2014, Visual MINTEQ 3.1. User's manual) was used to determine cation speciation and struvite, tricalcium phosphate, vivianite, and ferrous sulfide formation at a range of digestion conditions. Significant Mg and Ca complexation was predicted at all conditions evaluated, and the majority of the complexes were monovalent cations. Complexation reduced the divalent cation concentration on the order of 40%. The HRRSA and POTW B data both showed that dewatered cake total solids (TS) increased linearly with uncomplexed divalent cation concentration and that there was an increase of 1.0%-1.1% TS for every additional 1.0 meq/L of uncomplexed divalent cations. Because POTW B used centrifuge dewatering, this relationship could be independent of dewatering technique. Further, the relationship between uncomplexed divalent cation concentration and dewaterability suggests that the selectivity of exocellular polymeric substances cation exchange sites is much greater for divalent cations so that monovalent cations only bind to them when their concentrations are much higher than those of the uncomplexed divalent cations. Thus, monovalent cation concentration may not be important in anaerobic digestion or other high alkalinity environments. PRACTITIONER POINTS: It is important to account for complexation in high alkalinity environments such as anaerobic digesters; The findings of this study suggest that dewatering characteristics of anaerobically digested enhanced biological phosphorus removal (EBPR) waste sludge can be significantly improved by preserving cation-mediated exocellular polymeric substances bonding in the solids stream by reducing struvite formation; Data from two full-scale POTW's indicated that dewatered cake TS was increased by 1.0%-1.1% for every 1.0 meq/L of dissolved uncomplexed divalent cations in the anaerobic digestate bulk solution; This relationship existed for dewatering both by a belt filter press and by a centrifuge suggesting that this relationship is independent of dewatering technology; Dissolved monovalent cation concentrations may not be important in anaerobic digestion or other high alkalinity environments unless their concentrations are much greater than those of the dissolved divalent cations.