Rate Constants For Hydrolysis Research Articles

Transition State Mimic of Intrinsic Hydrolysis in Ras GTPase

Ras GTPases are involved in signal transduction pathways that control fundamental cellular processes such as proliferation, cycling, survival, and apoptosis. Ras functions via an on/off switch mechanism, where Ras is active in downstream signaling when bound to GTP and inactive upon GTP hydrolysis to GDP. Our lab discovered an allosteric site that is proposed to interact with the membrane, where binding in this allosteric site promotes ordering of the switch II region, favoring a conformation conducive to hydrolysis of GTP to GDP. When Ca2+ and acetate bind at this site in Ras crystals there is a disorder to order transition in switch II, positioning catalytic residues in place for hydrolysis. Interestingly, mutations of R97 to bulky aliphatic residues, such as L and M, mimic this effect, increasing hydrolysis rate constants relative to wild type. We had previously shown that in the presence of AlF3 RasR97L‐GDP binds to the Ras binding domain of Raf (Raf‐RBD), mimicking the γ‐phosphate of GTP. Here we present gel filtration studies of the R97M‐GDP mutant in the presence of Raf and AlF3 showing complex formation. The fact that Raf‐RBD binds to the R97L and R97M mutants, but not to wild type Ras, suggests that in these mutants the conformation associated with hydrolysis is more populated than in the wild type. AlFx has been used extensively to visualize the transition state of the GAP‐catalyzed GTP hydrolysis on Ras and its homologues. We are currently working on obtaining crystals of the H‐RasR97M‐Raf‐AlFx complex as a transition state model to elucidate the mechanism of intrinsic hydrolysis in Ras.Support or Funding InformationNSF MCB‐1517295

Base hydrolysis of α-amino acid esters catalysed by [Pd(N-ethylethylenediamine)(H2O)2]2+. Kinetic study and DFT calculations

Amino acid esters (L) react with [Pd(Eten)(H2O)2]2+ (Eten=N-ethyl ethylenediamine) giving mixed ligand complexes of the type [Pd(Eten)L]2+. Base hydrolysis of [Pd(Eten)L]2+ was studied by pH-stat technique from which rate constants for the base hydrolysis of the esters were obtained. The glycine methyl ester hydrolysed significantly, whereas the methionine methyl and histidine methyl esters hydrolysed much slower. The mode of coordination of the ester plays a role in the catalysis, and possible mechanisms for these reactions are considered. Activation parameters were determined for the hydrolysis of the glycine methyl ester. The effect of the dielectric constant of the medium on the hydrolysis process was also investigated. The B3LYP/LANL2DZ method was used for geometric optimization of the free ligand and the complex using the Gaussian 09 program. The calculations are compared with the kinetic data. In addition, the vibrational frequencies of the molecules were computed for the optimized geometries.

The acid-catalyzed hydrolysis of an <i>α</i>-pinene-derived organic nitrate: kinetics, products, reaction mechanisms, and atmospheric impact

Abstract. The production of atmospheric organic nitrates (RONO2) has a large impact on air quality and climate due to their contribution to secondary organic aerosol and influence on tropospheric ozone concentrations. Since organic nitrates control the fate of gas phase NOx (NO + NO2), a byproduct of anthropogenic combustion processes, their atmospheric production and reactivity is of great interest. While the atmospheric reactivity of many relevant organic nitrates is still uncertain, one significant reactive pathway, condensed phase hydrolysis, has recently been identified as a potential sink for organic nitrate species. The partitioning of gas phase organic nitrates to aerosol particles and subsequent hydrolysis likely removes the oxidized nitrogen from further atmospheric processing, due to large organic nitrate uptake to aerosols and proposed hydrolysis lifetimes, which may impact long-range transport of NOx, a tropospheric ozone precursor. Despite the atmospheric importance, the hydrolysis rates and reaction mechanisms for atmospherically derived organic nitrates are almost completely unknown, including those derived from α-pinene, a biogenic volatile organic compound (BVOC) that is one of the most significant precursors to biogenic secondary organic aerosol (BSOA). To better understand the chemistry that governs the fate of particle phase organic nitrates, the hydrolysis mechanism and rate constants were elucidated for several organic nitrates, including an α-pinene-derived organic nitrate (APN). A positive trend in hydrolysis rate constants was observed with increasing solution acidity for all organic nitrates studied, with the tertiary APN lifetime ranging from 8.3 min at acidic pH (0.25) to 8.8 h at neutral pH (6.9). Since ambient fine aerosol pH values are observed to be acidic, the reported lifetimes, which are much shorter than that of atmospheric fine aerosol, provide important insight into the fate of particle phase organic nitrates. Along with rate constant data, product identification confirms that a unimolecular specific acid-catalyzed mechanism is responsible for organic nitrate hydrolysis under acidic conditions. The free energies and enthalpies of the isobutyl nitrate hydrolysis intermediates and products were calculated using a hybrid density functional (ωB97X-V) to support the proposed mechanisms. These findings provide valuable information regarding the organic nitrate hydrolysis mechanism and its contribution to the fate of atmospheric NOx, aerosol phase processing, and BSOA composition.

Hydrothermal Degradation of Rutin: Identification of Degradation Products and Kinetics Study.

The model glycoside compound quercetin-3-O-rutinoside (rutin) was subjected to subcritical water within the temperature range of 120-220 °C, and the hydrothermal degradation products were analyzed. Two kinetic models describing the degradation of this compound in two different atmospheres (N2 and CO2), used for pressure establishment in the reactor, have been developed and compared. Reaction was considered a successive one with three irreversible steps. We confirmed that rutin degradation to quercetin follows first-order kinetics. At higher temperatures quercetin is further degraded in two degradation steps. Formations of 3,4-dihydroxybenzoic acid and catechol were described with the zero-order kinetic models. Reaction rate constants for hydrolysis of glycoside to aglycone in a CO2 atmosphere are higher compared to those in a N2 atmosphere, whereas at higher temperatures reaction rate constants for further two successive reactions of aglycone degradation are slightly lower in the presence of CO2. The difference in reaction activation energies is practically negligible for both gases. Furthermore, degradation products of sugar moieties, that is, 5-hydroxymethylfurfural and 5-methylfurfural, were also detected and analyzed.

Demasking kinetics of peptide bond cleavage for whey protein isolate hydrolysed by Bacillus licheniformis protease

During enzymatic hydrolysis of proteins, some cleavage sites will be accessible in the intact protein. Others may only become accessible after demasking of the cleavage site, i.e. after cleavage of other bonds in the protein. Studies on demasking so far have used data of the release of few peptides in a hydrolysate. To obtain a more complete understanding of the hydrolysis kinetics and to validate the demasking model, this study used the absolute quantification of all peptides formed during hydrolysis of whey protein isolate by Bacillus licheniformis protease. This allowed the determination of the rate constants of hydrolysis of each individual cleavage site in the substrate protein. For five cleavage sites, no cleavages were found. For nine cleavage sites, the hydrolysis was best described with first order kinetics addition. The other 13 cleavage sites were better described with the two-step demasking model, which consists of two consecutive first order reaction equations. In this way, the demasking concept was validated, showing that some peptide bonds are only cleaved when present in intermediate peptides.

Poly(malic acid-co-L-lactide) as a superb degradation accelerator for Poly(l-lactic acid) at physiological conditions

The effectiveness of poly(aspartic acid-co-l-lactide) (PAL) and poly(malic acid-co-l-lactide) (PML) oligomers as degradation accelerators for poly(l-lactic acid) (PLLA) was investigated in a phosphate buffer solution at 40 °C. It was found that the hydrolysis rate constant of the PLLA at 20 wt% loading is enhanced 15 times by PAL and 34 times by PML. The superiority of PML to PAL is probably related to its higher ability as acidic catalyst and higher miscibility with PLLA. Since PML and its decomposition products are environmentally safe and biocompatible, the present study demonstrates that PML is a promising biomaterial as a carrier matrix for biopharmaceuticals and for tissue regeneration. Our findings also proved the usefulness of PLLA blends containing a degradation accelerator in applications necessary to tune the degradation rate, since the blends are much easier to tailor the degradation rate compared to conventional PLLA copolymers such as poly(lactide-co-glicolide).

Alkaline-assisted screw press pretreatment affecting enzymatic hydrolysis of wheat straw.

Screw press processing of biomass can be considered as a suitable mechanically based pretreatment for biofuel production since it disrupts the structure of lignocellulosic biomass with high shear and pressure forces. The combination with chemical treatment has been suggested to increase the conversion of lignocellulosic biomass to fermentable sugars. Within the study, the synergetic effect of alkaline (sodium hydroxide, NaOH) soaking and screw press pretreatment on wheat straw was evaluated based on, e.g., sugar recovery and energy efficiency. After alkaline soaking (at 0.1M for 30min) and sequential screw press pretreatment with various screw press configurations and modified screw barrel, the lignin content of pretreated wheat straw was quantified. In addition, the structure of pretreated wheat straw was investigated by scanning electron microscopy and measurement of specific surface area. It could be shown that removal of lignin is more important than increase of surface area of the biomass to reach a high sugar recovery. The rate constant of the enzymatic hydrolysis increased from 1.1×10-31/h for the non-treated material over 2.3×10-31/h for the alkaline-soaked material to 26.9×10-31/h for alkaline-assisted screw press pretreated material, indicating a nearly 25-fold improvement of the digestibility by the combined chemo-mechanical pretreatment. Finally, the screw configuration was found to be an important factor for improving the sugar recovery and for reducing the specific energy consumption of the screw press pretreatment.

Fresh banana pseudo-stems as a tropical lignocellulosic feedstock for methane production

The banana pseudo-stem is a low-lignin-content lignocellulosic biomass that can be used for methane production. In recent years, anaerobic digestion (AD) of dried banana stems for methane production has attracted considerable attention. However, there is limited information regarding methane production from the fresh banana pseudo-stem. The direct usability of fresh banana stems as a resource for renewable energy production through AD is a called upon prerequisite for an improved waste management system culminating in a sustainable as well as socioeconomic development of local banana-producing communities. In this study, three series of experiments were performed simultaneously to investigate the methane production from fresh banana pseudo-stems for the first time. The tests included size reduction, enzyme addition, and co-digestion of banana stems with cow manure. The achieved methane yields were 287, 340, to 347 mL g−1 volatile solids for the banana stem with particle sizes of 5, 10, and 20 mm, respectively. The highest yield was obtained at the particle size of 20 mm, showing a 21 % increase compared to the particle size of 5 mm. However, the particle size of 5 mm showed a high initial rate of hydrolysis evident by the highest hydrolysis rate constant of 0.152 d−1 as compared to 0.110 d−1 for the 20-mm particle size. The addition of enzyme and co-digestion improved the rate of hydrolysis evident by a high rate constant as compared to the control though there was no improvement in the ultimate methane production. This study demonstrates the usability of the fresh banana stem for efficient and high methane production after simply applying a minimal size reduction. The implementation of such a study will benefit society especially rural banana-producing areas both toward renewable energy generation and sustainable waste management. These could lead to job creation and an improved standard of living.

Effects of pungency degree on mesophilic anaerobic digestion of kitchen waste

This study investigated the influence of pungency degrees (PDs) on mesophilic anaerobic digestion of kitchen waste (KW). Batch tests were performed to evaluate the methane potential and production rate and the effect of PDs on organics degradation efficiency (in terms of volatile solids, protein and ether extract) at mesophilic temperature. Koch and Drewes model and modified Gompertz model were applied to assess the effects of PDs on the hydrolysis rate constant, biomethane yield rate and lag time. The results revealed that with the increasing contributions of PDs, the methane yield, organics degradation efficiency and hydrolysis rate of KW decreased while the pH values and concentrations of total ammonia nitrogen and free ammonia nitrogen were increased. Additionally, PDs lower than PD3 presented better digestion performance, and according to results of organics degradation and kinetics study, it could be suggested that appropriate range of PD in KW beneficial for AD is PD5–PD4.

Hydrolysis rate constants at 10–25 °C can be more than doubled by a short anaerobic pre-hydrolysis at 35 °C

Hydrolysis is the first step of the anaerobic digestion of complex wastewater and considered as the rate limiting step especially at low temperature. Low temperature (10–25 °C) hydrolysis was investigated with and without application of a short pre-hydrolysis at 35 °C. Batch experiments were executed using cellulose and tributyrin as model substrates for carbohydrates and lipids. The results showed that the low temperature anaerobic hydrolysis rate constants increased by a factor of 1.5–10, when the short anaerobic pre-hydrolysis at 35 °C was applied. After the pre-hydrolysis phase at 35 °C and decreasing the temperature, no lag phase was observed in any case. Without the pre-hydrolysis, the lag phase for cellulose hydrolysis at 35–10 °C was 4–30 days. Tributyrin hydrolysis showed no lag phase at any temperature. The hydrolysis efficiency of cellulose increased from 40 to 62%, and from 9.6 to 40% after 9.1 days at 15 and 10 °C, respectively, when the pre-hydrolysis at 35 °C was applied. The hydrolysis efficiency of tributyrin at low temperatures with the pre-hydrolysis at 35 °C was similar to those without the pre-hydrolysis. The hydrolytic activity of the supernatant collected from the digestate after batch digestion of cellulose and tributyrin at 35 °C was higher than that of the supernatants collected from the low temperature (≤25 °C) digestates.

Water-soluble cavitands promote hydrolyses of long-chain diesters

Water-soluble, deep cavitands serve as chaperones of long-chain diesters for their selective hydrolysis in aqueous solution. The cavitands bind the diesters in rapidly exchanging, folded J-shape conformations that bury the hydrocarbon chain and expose each ester group in turn to the aqueous medium. The acid hydrolyses in the presence of the cavitand result in enhanced yields of monoacid monoester products. Product distributions indicate a two- to fourfold relative decrease in the hydrolysis rate constant of the second ester caused by the confined space in the cavitand. The rate constant for the first acid hydrolysis step is enhanced approximately 10-fold in the presence of the cavitand, compared with control reactions of the molecules in bulk solution. Hydrolysis under basic conditions (saponification) with the cavitand gave >90% yields of the corresponding monoesters. Under basic conditions the cavitand complex of the monoanion precipitates from solution and prevents further reaction.

A kinetic modeling for the ultrasound-assisted and oxalic acid-catalyzed hydrolysis of 3-glycidoxypropyltrimethoxysilane

Instantaneous hydrolysis rates of the ultrasound-assisted and oxalic acid-catalyzed hydrolysis of 3-glycidoxypropyltrimethoxysilane (GPTMS) have been obtained at several temperatures by using a dynamic ultrasound-adapted calorimetric method. Hydrolysis starts by ultrasound action because of the initial immiscibility gap between GPTMS and water. The hydrolysis process is a complex result of dissolution between GPTMS and H2O, which increases the hydrolysis rate, and reaction within the phases, which diminishes the hydrolysis rate as the reactants are consumed. The experimental hydrolysis rates were very well fitted by a modified version of an earlier kinetic model based on a dissolution and reaction mechanism. The rate constants for the ultrasound and methanol producing dissolution and the rate constants for the GPTMS hydrolysis were obtained by fitting the modeling to the overall heterogeneous/homogeneous hydrolysis pathway at each temperature studied. The hydrolysis rate constants were found in good agreement with those obtained previously on basis of a non-modeling method applied exclusively to the final homogeneous step of the reaction. Ultrasound producing mixture was found much more effective than methanol producing dissolution during the heterogeneous step of the GPTMS hydrolysis.

Effective cleavage of phosphodiester promoted by the zinc(II) and copper(II) inclusion complexes of β-cyclodextrin

To construct the model of metallohydrolase, two inclusion complexes [MLCl2(β-CD)] (1, M=Zn(II); 2, M=Cu(II); L=N,N′-bis(2-pyridylmethyl)amantadine; β-CD=β-cyclodextrin) were synthesized by mixing β-CDs with the pre-synthesized complexes G1, [ZnLCl2] and G2, [CuLCl2]. Structures of G1, G2, 1 and 2 were characterized by X-ray crystallography, respectively. In solution, two chloride anions of G1 and G2 underwent ligand exchange with solvent molecules according to ESI-MS analysis. The chemical equilibrium constants were determined by potentiometric pH titration. The kinetics of bis(4-nitrophenyl) phosphate (BNPP) hydrolysis catalyzed by G1, G2, 1 and 2 were examined at pHs ranging from 7.50 to 10.50 at 308±0.1K. The pH profile of rate constant of BNPP hydrolysis catalyzed by 1 exhibited an exponential increase with the second-order rate constant of 2.68×10−3M−1s−1 assigned to the di-hydroxo species, which was approximately an order of magnitude higher than those of reported mono-Zn(II)-hydroxo species. The high reactivity was presumably hydroxyl-rich microenvironment provided by β-CDs, which might effect in stabilizing either the labile zinc-hydroxo species or the catalytic transition state.

Determination of kinetic parameters for casein hydrolysis by chymotrypsin using two ranges of substrate concentration

Hydrolysis of casein by chymotrypsin was performed at low and high substrate concentrations. Hydrolysis kinetics were analysed in the framework of a two-step model, with consecutive demasking and hydrolysis steps. This model took into consideration the limited accessibility of peptide bonds for the enzyme (masking effect). Dependence of the logarithm of the hydrolysis rate via degree of hydrolysis was non-linear at concentrations of 0.04 and 10 g L−1. In the intermediate range of substrate concentrations (0.07–0.72), this dependence was found to be linear, corresponding to the exponential model of proteolysis. Taking into consideration the multiplicity of peptide bonds, coupled to peptide bond demasking, allowed determination of two important parameters: the ratio of the rate constants of demasking and hydrolysis (kd/kh), and the fraction of initially masked bonds (m). An analytical procedure was suggested for the calculation of the apparent Michaelis constants at various degrees of hydrolysis.

Carboxylic acid ester hydrolysis rate constants for food and beverage aroma compounds

AbstractAroma compounds in the Flavornet database were screened for potentially hydrolysable carboxylic acid ester functionalities. Of 738 aroma compounds listed in this database, 140 molecules contain carboxylic acid ester groups that may be amenable to hydrolysis in various food and beverage products. Acid‐ (kA) and base‐ (kB) catalysed and neutral (kN) hydrolysis rate constants in pure water at 25°C were calculated for these aroma compounds. Where available, good agreement between theoretical and experimental hydrolytic half‐lives was obtained at various pH values. Wide ranges and broad frequency distributions for kA, kB, and kN are expected among the various hydrolyzable aroma compounds, with calculated kA ranging from 3.7 × 10‐8 to 4.7 × 10‐4 M‐1 s‐1, calculated kB ranging from 4.3 × 10‐4 to 43 M‐1 s‐1, and calculated kN ranging from 4.2 × 10‐17 to 7.6 × 10‐9 M‐1 s‐1. The resulting hydrolytic half‐lives also range widely, from 10 days to 370 years at pH 2.8, 18 days to 4,900 years at pH 4.0, 1.8 days to 470 years at pH 7.0, and 26 minutes to 5.1 years at pH 9.0. The findings illustrate the importance of considering abiotic hydrolysis and matrix pH when modelling the evolution of sensory characteristics for foods and beverages with carboxylic acid ester based aroma compounds. Copyright © 2016 John Wiley & Sons, Ltd.

Site- and species-specific hydrolysis rates of heroin

The hydroxide-catalyzed non-enzymatic, simultaneous and consecutive hydrolyses of diacetylmorphine (DAM, heroin) are quantified in terms of 10 site- and species-specific rate constants in connection with also 10 site- and species-specific acid-base equilibrium constants, comprising all the 12 coexisting species in solution. This characterization involves the major and minor decomposition pathways via 6-acetylmorphine and 3-acetylmorphine, respectively, and morphine, the final product. Hydrolysis has been found to be 18–120 times faster at site 3 than at site 6, depending on the status of the amino group and the rest of the molecule. Nitrogen protonation accelerates the hydrolysis 5–6 times at site 3 and slightly less at site 6.Hydrolysis rate constants are interpreted in terms of intramolecular inductive effects and the concomitant local electron densities. Hydrolysis fraction, a new physico-chemical parameter is introduced and determined to quantify the contribution of the individual microspecies to the overall hydrolysis. Hydrolysis fractions are depicted as a function of pH.

Synthesis and Studies of N, N‐(Dimethylamino) Methylene Prodrugs of Gemcitabine, Ara‐A and Ara‐G

There is a need for developing prodrugs of nucleoside analogs to overcome limitations of permeability and bioavailability. One approach to nucleoside modification is by replacing the exocyclic amino groups on the nucleoside bases of adenosine, guanosine and cytidine with N, N‐(dialkylamino) methylene side chains to form their analogous amidine prodrug derivatives to improve their lipophilicity. In this study, the N, N‐(dimethylamino) methylene prodrugs of gemcitabine, 9‐β‐D‐arabinofuranosyladenine (Ara‐A), and 9‐β‐D‐arabinofuranosyl guanine (Ara‐G) were synthesized and their log P and hydrolysis rate constants were compared to 2′‐deoxycytidine and Ara‐C. Partition coefficients between 1‐octanol and the phosphate buffer saline (PBS) for all compounds were measured using the shake‐flask procedure. The lipophilicity of the prodrugs ranged from 1 to 1.5 fold more than the parent unmodified nucleoside. The hydrolytic pseudo‐first order rate constants were determined spectrophotometrically in PBS at 37 deg C. The hydrolytic studies indicated conversion of the prodrugs to the parent drugs was spontaneous with corresponding half‐lives of the prodrug ranging from 3 to more than 14 h. The dimethylamino‐methylene pro‐drug derivatives of Ara–G and Ara‐A were found to be more stable than the corresponding cytosine analogs. The Ara‐G prodrug derivative was the most stable derivative in terms of hydrolysis to its parent nucleoside. Cytotoxicity studies in an MCF‐7 cell line showed limited cytotoxic activity. These studies provide a basis to modulate the lipophilicity and hydrolytic stabilities of such nucleosides by varying the N,N‐dialkyl substitution to give derivatives with greater lipophilicity and stability.Support or Funding InformationSupported by the Graduate Studies Department of MCPHS University and Saudi Arabian Cultural Mission

On-line Study of Aesculin and Aesculetin Hydrolysis Using Sweeping-Flow Injection-chip Micellar Electrokinetic Chromatography

Aesculin and aesculetin hydrolysis were studied on-line using sweeping-flow injection-chip micellar electrokinetic chromatography (Sweeping-FI-chip MEKC). With this method, all the analytes in the sample are well separated within 5 min, and a sampling rate of 12 per hour is achieved. At this sampling frequency, a rate constant can be obtained within 30 min. In contrast to off-line methods, it was quite time. saving. And the aesculin hydrolysis mixture solution is directly injected and analyzed without quenching the reaction, thus the information of the hydrolysis process can be obtained from the electrophorogram of a sequence injection. Under the optimum conditions, the hydrolysis rate constants for aesculin at 25, 30, 35, 40 and 45 degrees C using 0. 1 mol/L KOH as hydrolyte are obtained as 3. 65 x 10(-2) /min, 5. 24 x 10(-2) /min, 7. 12 x 10(-2) /min, 10. 5 x 10(-2) /min and 16. 3 x 10(-2) /min, respectively. The activation energy for aesculin hydrolysis is 58. 57 kJ/mol. The hydrolysis rate constants for aesculetin at 15, 20, 25, 30 and 35. using 10 mmol/L KOH as hydrolyte are obtained as 2. 26 x 10(-2) /min, 2. 85 x 10(-2) /min, 3. 55 x 10(-2) /min, 4. 38 x 10(-2) /min and 5. 29 x 10(-2) /min, respectively. The activation energy for aesculin hydrolysis is 31. 55 kJ/mol.

Effects of thermal pretreatment on the biomethane yield and hydrolysis rate of kitchen waste

In this study, batch tests were performed to evaluate the effects of different thermal pretreatment temperatures (55–160°C) and durations (15–120min) on the anaerobic digestion of kitchen waste (KW). Two commonly used approaches, namely the modified Gompertz model and the approach developed by Koch and Drewes, were applied to assess the effects of the different pretreatment parameters on the biomethane yield, lag time and hydrolysis rate constant via data fitting. The subsequent anaerobic digestion of KW pretreated at 55–120°C presented greater efficiency, and longer treatment durations resulted in increased methane production and higher hydrolysis rate constants. These findings were obtained due to the lower nutrient loss observed in KW treated at lower temperature treatments compared with that found with higher temperature treatments. In general, the effects of thermal pretreatment on the lag phase and hydrolysis rate differed depending on the treatment parameters leading to the variations in the KW compositions. The soundness of the two model results was evaluated, and higher statistical indicators (R2) were found with the modified Gompertz model than with the approach developed by Koch and Drewes.

Use of the SPARC software program to calculate hydrolysis rate constants for the polymeric brominated flame retardants BC-58 and FR-1025

ABSTRACTThe SPARC software program was used to estimate the acid-catalyzed, neutral, and base-catalyzed hydrolysis rate constants for the polymeric brominated flame retardants BC-58 and FR-1025. Relatively rapid hydrolysis of BC-58, producing 2,4,6-tribromophenol—and ultimately tetrabromobisphenol A—as the hydrolytically stable end products from all potential hydrolysis reactions, is expected in both environmental and biological systems with starting material hydrolytic half-lives (t1/2,hydr) ranging from less than 1 h in marine systems, several hours in cellular environments, and up to several weeks in slightly acid fresh waters. Hydrolysis of FR-1025 to give 2,3,4,5,6-pentabromobenzyl alcohol is expected to be slower (t1/2,hydr less than 0.5 years in marine systems up to several years in fresh waters) than BC-58, but is also expected to occur at rates that will contribute significantly to environmental and in vivo loadings of this compound.