Deciphering Structural Traits for Thermal and Kinetic Stability across Protein Family Evolution through Ancestral Sequence Reconstruction.

Natural proteins are frequently marginally stable, and an increase in environmental temperature can easily lead to unfolding. As a result, protein engineering to improve protein stability is an area of intensive research. Nonetheless, since there is usually a high degree of structural homology between proteins from thermophilic organisms and their mesophilic counterparts, the identification of structural determinants for thermoadaptation is challenging. Moreover, in many cases, it has become clear that the success of stabilization strategies is often dependent on the evolutionary history of a protein family. In the last few years, the use of ancestral sequence reconstruction (ASR) as a tool for elucidation of the evolutionary history of functional traits of a protein family has gained strength. Here, we used ASR to trace the evolutionary pathways between mesophilic and thermophilic kinases that participate in the biosynthetic pathway of vitamin B1 in bacteria. By combining biophysics approaches, X-ray crystallography, and molecular dynamics simulations, we found that the thermal stability of these enzymes correlates with their kinetic stability, where the highest thermal/kinetic stability is given by an increase in small hydrophobic amino acids that allow a higher number of interatomic hydrophobic contacts, making this type of interaction the main support for stability in this protein architecture. The results highlight the potential benefits of using ASR to explore the evolutionary history of protein sequence and structure to identify traits responsible for the kinetic and thermal stability of any protein architecture.

Ocular cicatricial pemphigoid: is there an association with autoimmune diseases?

PURPOSE: To assess the prevalence of autoimmune diseases (ADs) associated with ocular cicatricial pemphigoid (OCP) and analyze clinical, laboratory, and treatment associations between these entities. METHODS: A multicentre cross-sectional study of patients with an OCP diagnosis. The population was divided into two groups according to their association with other ADs or not. Clinical, laboratory and treatment variables were described and compared between groups. A multivariable logistic regression analysis was performed to identify variables that could suggest the association between OCP and ADs. RESULTS: Eighty-eight patients were recruited, with a mean age at diagnosis of 64.3 years (SD 11.9). Biopsy was performed in 86.8% of the patients. There was a median delay of 2 years from the onset of symptoms to diagnosis. Extraocular involvement was evidenced in 11.5%. The group associated with ADs included 24 patients (27.3%). The most prevalent diagnosis was Sjögren´s syndrome. Hypergammaglobulinemia was associated with ADs and OCP, adjusted for age, sex, smoking, skin and mucosal involvement, and erythrocyte sedimentation rate (OR 8.7; 95%CI 1.6-46.8; p = 0.012). CONCLUSIONS: Due to OCP's autoimmune nature, it could coexist with other ADs. This study observed that more than a quarter of the population presented with this association, and hypergammaglobulinemia could suggest it.

Significance of HLA-B[*]51 allele expression in Crohn's disease: a case-control study.

OBJECTIVES: Crohn's disease (CD) and Behçet's disease (BD) are two autoinflammatory diseases that share clinical and pathogenic features. Furthermore, when BD involves the gastrointestinal tract, it is extremely difficult to distinguish endoscopic lesions from CD lesions. HLA-B*51 allele expression is highly associated with BD diagnosis. In this study we analysed HLA-B*51 status in 70 Argentine patients with confirmed CD diagnosis and compared it to our previous Argentine BD cohort, with the aim of finding similarities or differences between these two diseases regarding HLA-B*51 status. METHODS: This is a multi-centre case-control study, including 70 patients with confirmed CD diagnosis, who underwent HLA-B*51 allele status testing; the results were compared to our previous BD cohort of 34 patients. RESULTS: Among patients with CD, 12.85% were positive for the HLA-B*51 allele, compared with 38.24% patients with BD (OR=0.238; 95% CI=0.089-0.637; p=0.004). CONCLUSIONS: Our finding suggests that determination of HLA-B*51 allele status may contribute to the differential diagnosis between CD and BD.

Structure of an ancestral ADP-dependent kinase with fructose-6P reveals key residues for binding, catalysis, and ligand-induced conformational changes.

ADP-dependent kinases were first described in archaea, although their presence has also been reported in bacteria and eukaryotes (human and mouse). This enzyme family comprises three substrate specificities; specific phosphofructokinases (ADP-PFKs), specific glucokinases (ADP-GKs), and bifunctional enzymes (ADP-PFK/GK). Although many structures are available for members of this family, none exhibits fructose-6-phosphate (F6P) at the active site. Using an ancestral enzyme, we obtain the first structure of an ADP-dependent kinase (AncMsPFK) with F6P at its active site. Key residues for sugar binding and catalysis were identified by alanine scanning, D36 being a critical residue for F6P binding and catalysis. However, this residue hinders glucose binding because its mutation to alanine converts the AncMsPFK enzyme into a specific ADP-GK. Residue K179 is critical for F6P binding, while residues N181 and R212 are also important for this sugar binding, but to a lesser extent. This structure also provides evidence for the requirement of both substrates (sugar and nucleotide) to accomplish the conformational change leading to a closed conformation. This suggests that AncMsPFK mainly populates two states (open and closed) during the catalytic cycle, as reported for specific ADP-PFK. This situation differs from that described for specific ADP-GK enzymes, where each substrate independently causes a sequential domain closure, resulting in three conformational states (open, semiclosed, and closed).

Identification of new ethanol-tolerant yeast strains with fermentation potential from central Patagonia.

The quest for new wild yeasts has increasingly gained attention because of their potential ability to provide unique organoleptic characters to fermented beverages. In this sense, Patagonia offers a wide diversity of ethanol-tolerant yeasts and stands out as a bioprospecting alternative. This study characterized the genetic and phenotypic diversity of yeast isolates obtained from Central Chilean Patagonia and analyzed their fermentation potential under different fermentative conditions. We recovered 125 colonies from Nothofagus spp. bark samples belonging to five yeast species: Saccharomyces eubayanus, Saccharomyces uvarum, Lachancea cidri, Kregervanrija delftensis, and Hanseniaspora valbyensis. High-throughput microcultivation assays demonstrated the extensive phenotypic diversity among Patagonian isolates, where Saccharomyces spp and L. cidri isolates exhibited the most outstanding fitness scores across the conditions tested. Fermentation performance assays under wine, mead, and beer conditions demonstrated the specific potential of the different species for each particular beverage. Saccharomyces spp. were the only isolates able to ferment beer wort. Interestingly, we found that L. cidri is a novel candidate species to ferment wine and mead, exceeding the fermentation capacity of a commercial strain. Unlike commercial strains, we found that L. cidri does not require nutritional supplements for efficient mead fermentation. In addition, L. cidri produces succinic and acetic acids, providing a distinct profile to the final fermented product. This work demonstrates the importance of bioprospecting efforts in Patagonia to isolate novel wild yeast strains with extraordinary biotechnological potential for the fermentation industry.

Validation and adaptation of the Spanish version of the systemic lupus activity questionnaire (S-SLAQ) in an Argentinean population.

OBJECTIVES: To validate the systemic lupus activity questionnaire (SLAQ) in Spanish language. METHODS: The SLAQ questionnaire was translated and adapted in Spanish. Consecutive SLE patients from 8 centers in Argentina were included. A rheumatologist completed a Systemic Lupus Activity Measure (SLAM), Systemic Lupus Erythematosus Disease Activity Index (SLEDAI)-2K, and a physician's assessment. Reliability was assessed by internal consistency (Cronbach's alpha), stability by test-retest reliability (intraclass correlation coefficient), and construct validity by evaluating the correlation with clinically relevant scores. Sensitivity and specificity for clinically significant disease activity (SLEDAI ≥6) of different S-SLAQ cut-off points were evaluated. RESULTS: We included 97 patients ((93% female, mean age: 40 years (SD14.7)). Internal consistency was excellent (Cronbach's alpha = 0.84, p < 0.001), and the intraclass correlation coefficient was 0.95 (p < 0.001). Mean score of S-SLAQ was 8.2 (SD 7.31). Correlation of S-SLAQ was moderate with Patient NRS (r= 0.63 p< 0.001), weak with SLAM-no lab (r = 0.42, p <0.001) and SLAM (r = 0.38, p < 0.0001), and very weak with SLEDAI-2K (r = 0.15, p =0.1394). Using the S-SLAQ cutoff of five points, the sensitivity was 72.2% and specificity was 37.9%, for clinically significant disease activity. CONCLUSIONS: The S-SLAQ showed good validity and reliability. A good correlation, similar to the original instrument, was observed with patient´s global disease activity. No correlation was found between S-SLAQ and gold standard disease activity measures like SLEDAI-2K and SLAM. The S-SLAQ cutoff point of 5 showed a good sensitivity to identify the active SLE population and therefore could be an appropriate screening instrument for disease activity in clinical and epidemiological studies.

Phylogeographic reconstruction using air transportation data and its application to the 2009 H1N1 influenza A pandemic.

Influenza A viruses cause seasonal epidemics and occasional pandemics in the human population. While the worldwide circulation of seasonal influenza is at least partly understood, the exact migration patterns between countries, states or cities are not well studied. Here, we use the Sankoff algorithm for parsimonious phylogeographic reconstruction together with effective distances based on a worldwide air transportation network. By first simulating geographic spread and then phylogenetic trees and genetic sequences, we confirmed that reconstructions with effective distances inferred phylogeographic spread more accurately than reconstructions with geographic distances and Bayesian reconstructions with BEAST that do not use any distance information, and led to comparable results to the Bayesian reconstruction using distance information via a generalized linear model. Our method extends Bayesian methods that estimate rates from the data by using fine-grained locations like airports and inferring intermediate locations not observed among sampled isolates. When applied to sequence data of the pandemic H1N1 influenza A virus in 2009, our approach correctly inferred the origin and proposed airports mainly involved in the spread of the virus. In case of a novel outbreak, this approach allows to rapidly analyze sequence data and infer origin and spread routes to improve disease surveillance and control.

Novel function of transcription factor Uga3 as an activator of branched-chain amino acid permease BAP2 gene expression.

Gene regulation in yeast occurs at the transcription level, i.e. the basal level of expression is very low and increased transcription requires gene-specific transcription factors allowing the recruitment of basal transcriptional machinery. Saccharomyces cerevisiae BAP2 gene encodes the permease responsible for most uptake of leucine, valine and isoleucine, amino acids that this yeast can use as nitrogen sources. Moreover, BAP2 expression is known to be induced by the presence of amino acids such as leucine. In this context, the results presented in this paper show that BAP2 is an inducible gene in the presence of nitrogen-non-preferred source proline but exhibits high constitutive non-inducible expression in nitrogen-preferred source ammonium. BAP2 expression is regulated by the SPS sensor system and transcription factors Leu3, Gcn4 and Dal81. This can be achieved or not through a direct binding to the promoter depending on the quality of the nitrogen source. We further demonstrate here that an interaction occurs in vivo between Uga3 ‒ the transcriptional activator responsible for γ-aminobutyric acid (GABA)-dependent induction of the GABA genes ‒ and the regulatory region of the BAP2 gene, which leads to an increase in BAP2 transcription.

[COVID-19 infection presenting as a myocardial infarction. Report of one case]. / Paciente de 30 años con infarto agudo al miocardio e infección por SARS-CoV-2, presentación inhabitual de Covid-19. Caso clínico.

Isolated cardiac involvement of COVID-19 is an infrequent presentation, and myocardial infarction is even less common. We report a 30-year-old man presenting with retrosternal pain of insidious onset whose intensity increases suddenly. On admission, the patient had tachycardia and an EKG showed a 1 mm ST-elevation and diffuse PQ segment depression. Troponin was 26.9 ng/ml (normal value [NV] < 0.03), inflammatory parameters were elevated, and SARS-CoV 2 PCR was positive. He was hospitalized with the diagnosis of myopericarditis secondary to SARS-CoV 2. He progressed favorably without pain during the hospital stay and with decreasing troponin values. A Cardiac Magnetic Resonance Imaging (MRI) was compatible with an infero-lateral transmural infarction. A coronary angiography showed a distal occlusion of the circumflex artery. Consequently, anticoagulation and double platelet anti-aggregation were started. The patient evolved favorably, with a decreasing troponin curve (last at discharge 0.49 ng/ml) and a control EKG with pathological Q in DIII and AvF, and symmetrically inverted T in DII, DIII, AvF, V4, V5, and V6.

Assessing the quality of service for drinking water supplies in rural settings: A synthetic index approach.

In rural settings, the presence of water supply infrastructure does not guarantee that people will have access to dependable and high-quality drinking water. To evaluate deficiencies, an assessment of quality of service of rural drinking water supply systems (RDWSS) should be examined from a multi-criteria perspective, one that integrates economic, technical, administrative, and operational components of supplying water, which includes a variety of stakeholders to integrate their preferences in the development of a synthetic index. In this study, we followed a pioneering approach to evaluate the quality of service for RDWSS based on analytic hierarchy process (AHP) and Monte Carlo simulations. We empirically applied the approach to 40 RDWSS in Chile. The weights of a set of 14 performance indicators were allocated by representatives of the communities that manage the RDWSS and experts on technical and administrative issues revelling the different preferences of decision-makers. We found that there are significant differences in the quality of service provided by the RDWSS evaluated. The information provided by the synthetic indicator would be very helpful in supporting decision makers needing to prioritize investments among drinking water supplies in rural settings.

Structural insights into a functional unit from an immunogenic mollusk hemocyanin.

Mollusk hemocyanins, among the largest known proteins, are used as immunostimulants in biomedical and clinical applications. The hemocyanin of the Chilean gastropod Concholepas concholepas (CCH) exhibits unique properties, which makes it safe and effective for human immunotherapy, as observed in animal models of bladder cancer and melanoma, and dendritical cell vaccine trials. Despite its potential, the structure and amino acid sequence of CCH remain unknown. This study reports two sequence fragments of CCH, representing three complete functional units (FUs). We also determined the high-resolution (1.5 Å) X-ray crystal structure of an "FU-g type" from the CCHB subunit. This structure enables in-depth analysis of chemical interactions at the copper-binding center and unveils an unusual, truncated N-glycosylation pattern. These features are linked to eliciting more robust immunological responses in animals, offering insights into CCH's enhanced immunostimulatory properties and opening new avenues for its potential applications in biomedical research and therapies.

Clinical features and outcomes of 37 Argentinean patients with severe granulomatosis with polyangiitis (wegener granulomatosis).

BACKGROUND: Most epidemiologic studies involving severe granulomatosis with polyangiitis (SGPA) patients have investigated populations from the northern hemisphere, whereas few studies have been conducted in South America. None of the South American studies have differentiated between localized GPA and SGPA. PURPOSE: The present study was designed to describe a cohort of Argentinean patients who were diagnosed with SGPA and to compare this cohort with previously well-described cohorts. METHODS: We performed a retrospective study that included 37 consecutive SGPA patients who were seen at 2 tertiary centers in Buenos Aires. RESULTS: Nineteen patients (51.3%) were male, and 18 patients (49.7%) were female. The mean age at the onset of symptoms was 48.5 ± 12.01 years. Antineutrophil cytoplasmic antibody (ANCA) was detected in 34 patients (91.89%): 32 patients (86.48%) had a cytoplasmic staining pattern, whereas 2 patients (5.40%) had a perinuclear pattern. Three patients were ANCA-negative. Twenty-four patients (64%) achieved remission, and 7 patients (19%) had response as defined by at least 50% reduction in the disease activity score. Nineteen relapses were observed in 12 patients, and 2 of the relapses were fatal. Overall, there were 14 deaths (37.83%). CONCLUSIONS: The present series demonstrated that Argentinean patients have similar demographics, clinical manifestations, and outcomes as the cohorts from the northern hemisphere. There was less granulomatous organ involvement (ear/nose/throat, lung granulomas) in the present cohort compared with other series.

Behçet disease in Latin American countries: A systematic literature review of demographic and clinical features, and HLA-B*51 allele frequency.

OBJECTIVE: To describe the demographic and clinical features, as well as the frequency of the HLA-B*51 allele in Behçet disease (BD) patients in Latin American countries. METHODS: A systematic literature review of PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analysis) guidelines was conducted without performing a meta-analysis. We included observational studies (cross-sectional or cohort) of BD patients fulfilling the International Study Group for BD classification criteria and reported the demographic, clinical, and laboratory features of the disease in adult patients. RESULTS: Twelve studies were included in the SLR. Information from 532 patients across 5 Latin American countries was included for the analysis. Mean age at disease diagnosis was 33 years, 58.3% were female and 41.7% male; most patients were non-Caucasian. The most common clinical manifestations were recurrent oral ulcers and genital ulcers, followed by skin, eye, joint, neurological, gastrointestinal, vascular, and cardiac involvement. The prevalence of BD was described in 2 studies, 1 conducted in Brazil that reported a prevalence of .3/100,000 inhabitants, and another in Colombia with a prevalence of 1.1/100,000 inhabitants. The frequency of HLA-B*51 allele in BD patients was 38%, 30.1%, and 9% in Argentina, Brazil, and Mexico, respectively. CONCLUSIONS: The prevalence of BD in the Latin American countries seems to be low, as well as the frequency of HLA-B*51 allele. However, the strength of association between HLA-B*51 and BD remains high in our population. The key clinical features of BD are like those reported in countries/regions where BD is endemic.

Personal and Work-Related Burnout Is Associated with Elevated Diastolic Blood Pressure and Diastolic Hypertension among Working Adults in Chile.

We aimed at investigating the association of personal and work-related burnout with blood pressure and hypertension among working adults in Chile. We conducted a cross-sectional study among 1872 working adults attending the Hospital del Trabajador in Santiago, Chile, between September 2015 and February 2018. The Copenhagen Burnout Inventory was used to assess personal and work-related burnout. Blood pressure was measured by medical practitioners. Multivariable linear and logistic regressions were used to estimate the association of burnout status with systolic blood pressure (SBP), diastolic blood pressure (DBP), and hypertension. After adjusting for confounders, participants with both types of burnout had a 1.66 (95% confidence interval [CI]: 0.02-3.30) mmHg higher mean DBP than those without burnout. The odds of isolated diastolic hypertension among the participants with only personal burnout and both types of burnout were 2.00-fold (odds ratio [OR] = 2.00; 95% CI: 1.21-3.31) and 2.08-fold (OR = 2.08; 95% CI: 1.15-3.78) higher than those without burnout. The odds of combined systolic/diastolic hypertension among the participants with only work-related burnout increased by 59% (OR = 1.59; 95% CI: 1.01-2.50) compared with those without burnout. Both work-related and personal burnouts were associated with increased DBP and odds of diastolic hypertension among working adults in Chile.

Minipterional Approach for Middle Fossa Skull Base Lesions: Technical Note.

Surgical access to the middle fossa can be technically challenging. As neurosurgery evolves to minimally invasive approaches, the objective of this study is to demonstrate the extension of the Minipterional approach to access the middle fossa. We present a new surgical approach to the middle fossa for the treatment of secondary trigeminal neuralgia. Three cases are reported to illustrate the following techniques: a patient with petrotentorial meningioma and trigeminal neuralgia, a patient with an arachnoid cyst compressing the fifth nerve, and a patient with a middle cerebral artery aneurysm and a long history of TN (trigeminal neuralgia) refractory to medical and surgical treatments. All three experienced full symptom controls with no permanent neurological deficits. Therefore, the Minipterional technique might represent a feasible, effective, and safe option to treat refractory secondary TN. It also allows approaching these lesions when the posterior fossa approach is compromised by anatomical distortion and enables the simultaneous treatment of secondary trigeminal neuralgia and other lesions, such as aneurysms and meningiomas.

Immersive ultraviolet disinfection of E. coli and MS2 phage on woven cotton textiles.

Immersive ultraviolet disinfection provides a chemical-free technology for safer textiles, surfaces, and public spaces by inactivating communicable pathogens. This study examined immersive UV disinfection, using a disinfection cabinet, of E. coli and MS2 that was inoculated on white cotton T-shirts. The impact that porous materials have on UV disinfection is poorly understood with the majority of previous surface disinfection research focusing on hard, smooth surfaces. Several approaches were used in this study to characterize the light dynamics within the disinfection cabinet including colorimetric dosimetry coupons, biodosimetry, and spectroradiometry. Micro and macro geometry of porous surfaces are important factors to consider when using immersive UV technologies. The geometry of the cabinet impacted the distribution of emitted UV light within the disinfection cabinet and the physical properties of a porous material, such as the woven pattern of cotton, both contribute to UV disinfection efficiency. This work identified that light distribution is crucial for immersive UV technologies as the delivered fluence was highly variable within the disinfection cabinet and resulted in a difference of several logs of reduction for adjacent areas of T-shirt samples. Other inoculated areas achieved upwards of 1-log reductions values for MS2 and upwards of 2-log reductions for E. coli.

The complete mitochondrial genome of the roosterfish Nematistius pectoralis Gill 1862: Purifying selection in protein coding genes, organization of the control region, and insights into family-level phylogenomic relationships in the recently erected order Carangiformes.

The roosterfish Nematistius pectoralis is considered as one of the most magnificent sportfishes worldwide. This study developed the first genomic resource for this trophy-fish that is heavily targeted by the fly-fishing industry. The complete mitochondrial genome of N. pectoralis was assembled using short read sequences and analyzed in detail. The mitochondrial genome of N. pectoralis is 16,537 bp in length and comprises 13 protein-coding genes (PCGs), 2 ribosomal RNA genes (12S and 16S), and 22 transfer RNA genes. A long intergenic space 770 bp in length was assumed to be the d-loop or Control Region (CR). Most of the PCGs and tRNA genes are encoded in the l-strand. All PCGs are under purifying selection and atp8 and nad6 experienced the least selective pressure. All tRNAs exhibit a cloverleaf secondary structure except tRNA-Serine 1 that lacked the d-arm loop. The d-loop of N. pectoralis exhibits three domains commonly described in other fishes; extended terminal associated sequences (ETAS), central, and conserved sequence block (CSB). A ML phylogenetic reconstruction of the newly recognized order Carangiformes based on all 13 mitochondrial PCGs did not support the monophyly of this clade but recognized several families as monophyletic, including Bothidae, Carangidae, Istiophoridae, Latidae, Paralichthyidae, Polynemidae, and Rhombosoleidae. Nematistius pectoralis was sister to a clade composed of Toxotes chatareus (fam. Toxotidae) + Lactarius lactarius (fam. Lactariidae). This genomic resource developed for N. pectoralis will aid in improving our understanding of the population genomics of and strengthen conservation and management strategies in this remarkable trophy-fish.

New Opportunities in Heart Failure with Preserved Ejection Fraction: From Bench to Bedside and Back.

Heart failure with preserved ejection fraction (HFpEF) is a growing public health problem in nearly 50% of patients with heart failure. Therefore, research on new strategies for its diagnosis and management has become imperative in recent years. Few drugs have successfully improved clinical outcomes in this population. Therefore, numerous attempts are being made to find new pharmacological interventions that target the main mechanisms responsible for this disease. In recent years, pathological mechanisms such as cardiac fibrosis and inflammation, alterations in calcium handling, NO pathway disturbance, and neurohumoral or mechanic impairment have been evaluated as new pharmacological targets showing promising results in preliminary studies. This review aims to analyze the new strategies and mechanical devices, along with their initial results in pre-clinical and different phases of ongoing clinical trials for HFpEF patients. Understanding new mechanisms to generate interventions will allow us to create methods to prevent the adverse outcomes of this silent pandemic.

[Association between acute disseminated encephalomyelitis and Guillain-Barré syndrome in an adult]. / Asociación de encefalomielitis diseminada aguda y síndrome de Guillain-Barré en un adulto.

Acute disseminated encephalomyelitis (ADEM) and Guillain-Barré Syndrome (GBS) are commonly recognized as separated entities involving different parts of the nervous system. However, they share some features such as: autoimmune pathogenesis, myelin injury and previous history of viral infections or vaccination. We report the case of a 41 year-old man who developed fever, lower limbs weakness and obtundation fifteen days after an acute gastroenteritis. Neurological examination showed patellar hypereflexia, bilateral Babinski and neurogenic bladder. Twenty-four hours later he developed flaccid paraparesis, generalized areflexia and respiratory failure that was supported by mechanical ventilation. Cerebrospinal fluid showed mononuclear pleocytosis and elevated proteins. Electrodiagnosis showed important reduction of conduction velocity on both peroneal nerves. Magnetic Resonance Imaging revealed white matter lesions in brain, pons and thoracic levels of the spinal cord. Diagnosis of the association between ADEM and GBS (ASADEM-GBS) was made and treatment with corticosteroids and intravenous immunoglobulin was started. The patient recovered motor, sensory and bladder functions and he was able to walk six months later. ASADEM-GBS is an uncommon entity generally considered of poor outcome; however a rapid diagnosis and treatment can substantially improve the prognosis.

Impact of sodium silicate on lead release and colloid size distributions in drinking water.

Sodium silicates have been used in drinking water treatment for decades as sequestrants and corrosion inhibitors. For the latter purpose they are poorly understood, which presents a potential public health risk. We investigated a common sodium silicate formulation as a treatment for lead release and compared it to orthophosphate, a well-established lead corrosion control treatment. We also compared the size distributions of colloids generated in silicate and orthophosphate-treated systems using field flow fractionation with multielement detection. At a moderate dose of 24 mg SiO2/L, sodium silicate yielded a median lead release of 398 µg/L, while orthophosphate yielded 67 µg Pb/L. At an elevated dose of 48 mg SiO2/L, sodium silicate dispersed corrosion scale in cast iron pipe sections and lead service lines, resulting in a substantial release of colloidal iron and lead. In the silicate-treated system, a silicon-rich coating occurred at the lead-water interface, but lead carbonate remained the major corrosion product and appeared to control lead levels. These data suggest that, as a corrosion control treatment for lead, sodium silicate is inferior to orthophosphate in circumneutral pH water with low alkalinity. And, as with polyphosphate, excess silicate can be highly detrimental to controlling lead release.