Medium Molecular Weight Fractions Research Articles

Water-soluble compounds from Lignosus rhinocerus TM02® (xLr™) modulate ACE2 activity and inhibit its interaction with SARS-CoV-2 Spike-Protein

Water-soluble compounds from Lignosus rhinocerus TM02® (xLr™) modulate ACE2 activity and inhibit its interaction with SARS-CoV-2 Spike-Protein

Relating algal-derived extracellular and intracellular dissolved organic nitrogen with nitrogenous disinfection by-product formation

The dissolved organic nitrogen (DON) pool from algal-derived extracellular and intracellular organic matter (EOM and IOM) comprises proteins, peptides, free amino acids and carbohydrates, of which, proteins can contribute up to 100% of the DON. Previous reports of algal-derived DON character have focused on bulk properties including concentration, molecular weight and hydrophobicity. However, these can be similar between algal species and between the EOM and IOM even when the inherent molecular structures vary. A focus on bulk character presents challenges to the research on algal-derived nitrogenous-disinfection by-product (N-DBP) formation as N-DBP formation is sensitive to the changes in molecular structure. Hence, the main aim of this study was to characterize algal EOM and IOM-derived DON, specifically proteinaceous-DON, using a combination of bulk and molecular characterization techniques to enable a more detailed exploration of the relationship between the character of algal-derived proteins and the N-DBP formation potential. DON from the EOM and IOM of four commonly found algae and cyanobacteria in natural waters were evaluated, namely Chlorella vulgaris, Microcystis aeruginosa, Dolichospermum circinale, and Cylindrospermopsis raciborskii. It was observed that 77-96% of total DON in all EOM and IOM samples was of proteinaceous origin. In the proteins, DON concentrations were highest in the high molecular weight fraction of IOM-derived bulk proteins (0.13–0.75 mg N L−1) and low to medium molecular weight fraction of EOM-derived bulk proteins (0.15–0.63 mg N L−1) in all species. Similar observations were also made via sodium dodecyl sulphate polyacrylamide gel electrophoresis and liquid chromatography-high resolution mass spectrometry. Solid-state 15N nuclear magnetic resonance (NMR) spectroscopy of the EOM and IOM revealed the existence of common aliphatic and heterocyclic N-groups in all samples, including a dominant 2° amide peak. Species dependent variability was also observed in the spectra, particularly in the EOM; e.g. nitro signals were found only in the Cylindrospermopsis raciborskii EOM. Dichloroacetonitrile (DCAN) and N-nitrosamine concentrations from the EOM of the species evaluated in this study were lower than the guideline limits set by regulatory agencies. It is proposed that the dominant 2° amide in all samples decreased N-DBP formation upon chlorination. For chloramination, the presence of nitro groups and aliphatic and heterocyclic N-DBP precursors could cause variable N-nitrosamine formation. Compared to non-algal impacted waters, algae-laden waters are characterised by low organic carbon: organic nitrogen ratios of ∼7–14 and elevated DON and protein concentrations. Hence, relying only on bulk characterization increases the perceived risk of N-DBP formation from algae-laden waters.

Understanding the influence of pre-ozonation on the formation of disinfection byproducts and cytotoxicity during post-chlorination of natural organic matter: UV absorbance and electron-donating-moiety of molecular weight fractions.

Pre-ozonation can reduce the formation of disinfection byproducts (DBPs) and related adverse effects during subsequent chlorination, but the change of each molecular weight (MW) fraction during each step of combined pre-ozonation and post-chlorination has not been well illustrated. In this study, it was investigated in terms of electron-donating-moieties (EDMs) and UVA254 for a representative natural organic matter from Suwanee river (SRNOM). Pre-ozonation suppressed the post-chlorination of SRNOM through oxidation of almost all EDMs (>85%) and UVA254 (>90%) in high MW fractions (HMW, >3.2kDa) and moderate EDMs (43%) and UVA254 (72%) in medium MW fractions (MMW, 1.0-3.2kDa). Furthermore, pre-ozonation led to comparable abatements of EDMs and UVA254 for HMW fractions, but lower abatement of EDMs than UVA254 for MMW fractions. However, when t-BuOH was used as an •OH-quencher, pre-ozonation led to a few instances in which there were higher abatements of EDMs than UVA254 for the MMW fraction. These findings suggested that the HMW fraction dominantly underwent ring-cleavage of phenols via O3- or •OH-oxidation. Differently, the MMW fraction underwent ring-cleavage of phenols and quinones-formation via O3-oxidation, but occasionally underwent hydroxylation and hydro-phenol formation via •OH-oxidation. Because of forehand elimination of reactive moieties (e.g. EDMs), pre-ozonation obviously inhibited the formation of representative DBPs (67%-84% inhibition), total organic chloride (51% inhibition) and cytotoxicity (31% inhibition), but may have promoted the formation of carbonyl-DBPs (trichloroacetone and chloral hydrate). When compared with UVA254, EDMs would better for surrogate of DBPs formation. EDM abatement surrogated the formation of total organic chlorine (TOCl) and cytotoxicity following a two-stage phase, possibly because the speciation of DBPs and transformation products varied with the abatement of EDMs.

Comparison of UV/H2O2 and UV/PS processes for the treatment of reverse osmosis concentrate from municipal wastewater reclamation

Reverse osmosis concentrate (ROC) from municipal wastewater treatment contains high concentrations of complex toxic biorefractory pollutants. We studied the mechanisms by which two ultraviolet advanced oxidation processes, UV/H2O2 and UV/PS, degraded pollutants in ROC from municipal wastewater reclamation processes. Both technologies had similar removal efficiencies of bulk dissolved organic matter based on the observed reduction in COD, chromophores, and fluorophores. However, UV/PS decomposed both high and medium molecular weight (MW) fractions (57 and 67.7%), while UV/H2O2 preferentially decomposed only the high MW fraction (60 and 39.1%), suggesting that the two methods operate by different reaction mechanisms. The changes in electron donating capacity resulting from treatment by UV/H2O2 (42.3%) and UV/PS (75.2%) were different. SO4•− primarily decomposed compounds containing electron-donating groups better than •OH. The removal of dissolved organic matter by UV/PS resulted in decreases in both relative electron-donating capacity and relative specific ultraviolet absorbance. The distinct reaction mechanisms were observed between UV/PS and UV/H2O2, being that UV/PS preferentially decomposed the contaminants via electrophilic addition and hydroquinone generation, while UV/H2O2 preferentially decomposed the contaminants via phenolic-ring cleavage reactions. Changes in the UV absorbance (UVA254) and the fluorescence index (FI) were used to monitor the rate of elimination of toxic biocides in the ROC.

Effect of alkylaluminium on the regio- and stereoselectivity in copolymerization of isoprene and butadiene using TiCl4/MgCl2 type Ziegler-Natta catalyst

Alkylaluminums as one of the most important components of the heterogeneous MgCl2-supported (TiCl4/MgCl2) type Ziegler-Natta catalysts, play significant roles in yielding active species with varied regio- and stereoselectivity. Studying the contribution of alkylaluminums on the conjugated diene isoprene (Ip) and butadiene (Bd) copolymerizations with TiCl4/MgCl2 - alkylaluminum catalysts system is little reported. In this work, effects of various alkylaluminums including triethylaluminium (TEA), triisobutylaluminium (TiBA), diisobutylaluminium hydride (DiBAH) and diethylaluminum chloride (DEAC) on the copolymerization behaviors of Ip and Bd using the TiCl4/MgCl2 - alkylaluminum catalysts system, such as catalytic activity, active center numbers, butadiene incorporation, trans-1,4 stereoselectivity, molecular weight Mw as well as molecular weight distribution Mw/Mn of copolymers were first investigated. TEA with smaller size ethyl groups showed higher copolymerization activity, higher reducing ability and then yielding more active center numbers ([C*]/[Ti]) when compared with TiBA, DiBAH and DEAC. Microstructure of copolymers gradually transformed from the cis-1,4/trans-1,4 mixed structure in the initial polymerization period to the finally high trans-1,4 structure, indicating a transformation of the active center nature during the early polymerization stage, which can be accelerated effectively through the addition of DEAC into the TiCl4/MgCl2-TEA catalyst system. TEA with smaller size ethyl group showed higher transformation rate from the mixed structures of trans-1,4 and cis-1,4 to highly trans-1,4 structure. The active center numbers of the copolymerization systems increased gradually with increasing time until reaching a stable level. The Mw/Mn of copolymers showed interesting evolution with increasing polymerization time from broad distribution with low to medium molecular weight fractions in the initial polymerization stage to relatively narrow distribution with high molecular weight fractions. The contribution of alkylaluminium compounds on the structure of active species which determining the regio- and stereoselectivity of Ip and Bd copolymerization using heterogeneous TiCl4/MgCl2 type catalysts were discussed in details

Plasma adiponectin array in women with Alzheimer's disease.

Introduction Alzheimer's disease (AD) is a progressive and irreversible neurodegenerative disease. Typical features of AD include memory loss, social dysfunction and physical impairment. Although the pathological findings in the central nervous system are well established, the etiological factors are poorly known. Recent studies suggested the role of metabolic disturbances in the development of AD neurodegeneration. Adiponectin, an anti-inflammatory and metabolism regulating factor, was linked to AD. Aim The aim was to examine whether adiponectin fractions combined with insulin/insulin resistance-associated metabolic parameters correlate with AD progression. Material and methods The study comprised 98 women: 27 with moderate to severe AD, 31 with AD at early stage and 40 healthy controls, matched for age and BMI. To evaluate memory impairment, the MMSE was performed. Plasma total adiponectin and its high-, medium- and low molecular weights were measured with ELISA. Anthropometric, clinical and metabolic parameters were assessed. Correlations between adiponectin array and measured parameters were evaluated. Results In comparison to the controls, enhanced levels of total and medium molecular weight adiponectin characterized AD individuals. In AD, we found correlations between adiponectin array, and anthropometric and biochemical parameters. After adjustment to BMI, a significant increase of the total adiponectin and high- and medium molecular weight fractions was observed. A negative correlation between low molecular weight adiponectin and MMSE was found. Conclusions Our results indicate a possible link between adiponectin variations and AD. We hypothesize that changes in adiponectin profile observed in AD result from compensatory mechanism against neuropathological processes, as well as from adiponectin homeostasis impairment.

Formation of resistant starch from amylotype corn starch and determination of the functional properties

High amylose corn starch was hydrolysed with HCl at 40 °C for 0.5-2.0 h. Then the native and acid-modified starch samples were subjected to 2 different heat treatments (HT). In HT1, heat treated/autoclaved samples were dried after storage and in HT2, heat treated/autoclaved samples were dried without storage. Relative quantities of high- and medium-molecular weight fractions decreased and relative quantities of low-molecular weight fractions increased as a result of acid modification. Resistant starch (RS) contents of the acid-modified starches were between 15.7-16.4% and increased up to 29.4% due to HT1 and up to 17.5% due to HT2. The results indicated that RS contents of the high amylose starch can be increased by HT and storing prior to drying. Rapid ViscoAnalayser viscosity values decreased as the acid modification level increased. Water absorption and solubility values of the samples prepared with both heat treatments were higher than those of the native starch and hydrolysates. Emulsifying capacity/ stability values of soy protein solution supplemented with the hydrolysates and heat treated samples were higher than those supplemented with the native and heat treated native starch.

Analyses of trace metals, peptide ligands of trace metals and mercury speciation in home prepared bread

Bread represents an important source of trace elements in the human diet. This study is focused on home prepared bread in the Czech Republic. The amounts of Cu, Mo, Mn, Ni and Zn (total and soluble in Tris-HCl buffer, pH 7.5), Cd, Co, Fe, Pb and Tl (total only) as well as Hg (total and soluble in mercaptoethanol-HCl mixture) in raw materials and baked bread were determined using ICP-MS. Moreover, the speciation of elements was investigated using HPLC/ICP-MS. Isolated peptide ligands of the trace elements were analysed for amino acids and characterised by MALDI-MS. The concentrations of all elements were in accordance with Czech legislation. The solubility of the Ni species was not affected by the baking process, whereas the solubilities of Mo, Mn and Zn species decreased. Soluble mercury was found only in the inorganic form. The soluble species of Cu, Mo, Mn, Ni and Zn were found in two fractions with the apparent molecular weights of 1–2 kDa and 4–5 kDa. Ligands of trace metals isolated from these fractions contained appreciable amounts of Asx, Glx, Gly, Ser and Cys. No phytochelatin-like peptides were found in the MALDI-MS spectra of isolated ligands,. Using MALDI-MS/MS, the partial amino-acids sequences of peptide ligands were obtained, and the linkages of peptides and saccharides confirmed. The MS analysis of the trypsin digest of the medium molecular weight fraction revealed several proteins rich in cysteine (e.g., barwin and amylase inhibitors).

Antitumor activity of degraded products of lentinan: its correlation with molecular weight.

Lentinan, an antitumor polysaccharide from Lentinus edodes, was degraded to seven fractions by treatment with formic acid. The low molecular-weight fractions (I and II) showed no antitumor activity against sarcoma-180 solid-type tumor and the absorption maximum of Congo Red did not shift in their presence in 0.1M sodium hydroxide. The medium molecular-weight fraction III, which required the increase of doses (5 or 10 mg/kg) for inhibition of tumor growth, caused a little shift. On the other hand, the absorption maximum of Congo Red shifted largely by the presence of high molecular-weight fractions (IV approximately VII) which showed the inhibition ratio of over 95% in a dose of 1 mg/kg. Participation of molecular weight in the antitumor activity of polysaccharides which contain (1 leads to 3)-beta-D-glucan main chain was discussed.

The influence of α-amylase-hydrolysed barley starch fractions on the viscosity of low and high purity barley β-glucan concentrates

Gelatinized barley starch was hydrolysed using porcine pancreatic α-amylase for various time intervals and the hydrolysate fractionated according to molecular weight distribution (low, medium and high) by gel permeation chromatography. The effects of hydrolysed starch fractions (2.5%, w/w) on the solution viscosity of low- (∼50%, w/w) and high- (∼88%, w/w) purity barley β-glucan (0.75%, w/w,) at different temperatures (20 and 37 °C) were determined and compared to that of a control. The results indicated that none of the hydrolysed starch fractions significantly influenced the solution viscosity of high purity β-glucan. However, addition of the medium molecular weight fraction to low purity β-glucan significantly increased its viscosity when determined at low shear rates (1.29–12.9 s −1). Marginal changes in viscosity were observed at shear rates exceeding 12.9 s −1. This study suggested that a non-β-glucan component in the low purity β-glucan concentrate probably influences the solution viscosity of “β-glucan–hydrolysed starch” blends.

Analysis of selenized yeast for selenium speciation by size-exclusion chromatography and capillary zone electrophoresis with inductively coupled plasma mass spectrometric detection (SEC-CZE-ICP-MS)

A two-dimensional separation approach based on size-exclusion chromatography (SEC) followed by capillary zone electrophoresis (CZE) is proposed for the mapping of seleno-compounds in aqueous extracts of selenized yeast. The coupling of CZE with ICP-MS via a self-aspirating total consumption micronebulizer was optimized for the separation of Se species. Selenate, selenite, selenocystine, selenomethionine and selenoethionine could be baseline separated at pH 10.5 using a 10 mM phosphate buffer containing 0.8 mM cetyltriammonium bromide. Detection limits were 7–18 ng mL−1 for a 20 nL injection. The CZE-ICP-MS analysis of a yeast extract demonstrated the presence of many Se species, which all migrated less rapidly than any of the standards. The following difficulties occurred during the CZE-ICP-MS analysis of the SEC fractions of the extract: the recovery of the high-molecular Se-species from the electrophoretic capillary, the presence of a large number of compounds in the medium-molecular weight fraction and the presence of a single intense peak for the low-molecular weight fraction. Proteolysis of the high- and medium-molecular weight fractions dramatically improved the recovery of Se species from the capillary, resulting in several peaks in the CZE-ICP-MS electropherograms.

Polyurethanes from Alcell® lignin fractions obtained by sequential solvent extraction

Lignin-derived polyurethane films were synthesized by solution casting using three fractions of distinct molecular weight and chemical functionality from Alcell® lignin. A three-component system of lignin fraction, polyethylene glycol (PEG) of MW=400 g mol −1 and polymeric methyl-diisocyanate (MDI) was used. For each lignin fraction, the effects of varying the NCO/OH ratio and lignin content on the crosslink density, ultimate tensile properties and dielectric strength of the polyurethanes were studied. The crosslink density was found to increase with molecular weight of lignin. Strong polyurethanes were produced with the high molecular weight fraction of Alcell® lignin, but the polyurethanes from the medium molecular weight fraction appeared to be tougher and more flexible. For both the medium and high molecular weight fractions of Alcell® lignin used, polyurethanes produced with lignin contents above 35 wt% were found to be too brittle and glassy to be tested. A maximum of 18 wt% of the low molecular weight lignin fraction could be used to prepare polyurethanes. Any higher compositions attempted produced polyurethanes which were too brittle to be tested. For all three fractions, the dielectric constant of the polyurethanes, decreased with increasing lignin content or NCO/OH ratio.

Medium molecular weight pentastarch reduces reperfusion injury by decreasing capillary leak in an animal model of spinal cord ischemia

Purpose: The medium molecular weight fraction of pentastarch (HES-Pz) has been shown to decrease reperfusion injury to myocardium and brain by reducing capillary leak. This study was undertaken to assess the effects of HES-Pz on neurologic function, microvascular permeability, and spinal cord infarction after temporary aortic cross-clamping in a rabbit model. Methods: In 30 New Zealand White rabbits, a snare occlusion device was placed around the infrarenal aorta and tunneled into a subcutaneous position. Animals were allowed to recover for 48 hours and were randomized into three groups. In each group, the infrarenal aorta was occluded by tightening the snare in the awake animal for 21 minutes. Immediately after unclamping, animals received an intravenous infusion of 4% of their estimated blood volume of one of the following solutions: normal saline solution (NS; group 1); 6% standard hydroxyethyl starch (HES), molecular weight 10 to 3400 kD (group 2); and 6% HES-Pz, molecular weight 100 to 1000 kD (group 3). During 5 days of observation, neurologic recovery was graded by an independent observer using the Tarlov scale. Animals were then killed and their spinal cords harvested for histologic examination using hematoxylin-eosin and 2,3,5-triphenyltetrazolium chloride staining. In a separate group of animals (n = 15), the occurrence of spinal cord capillary permeability after NS, HES, and HES-Pz infusions was evaluated by spectrophotometric analysis of extravasated Evans blue. Results: Complete paraplegia and marked histologic evidence of spinal cord cellular injury were seen in 90% of group 1 (NS) and in 78% of group 2 (HES). Treatment with HES-Pz (group 3) resulted in full neurologic recovery in 89% of animals ( p < 0.05) and a threefold reduction of extravasated Evans blue compared with controls ( p < 0.05). Conclusions: These results indicate that microvascular hyperpermeability plays an important role in reperfusion injury to the spinal cord. Treatment with HES-Pz reduced the capillary permeability, neuron membrane injury, and incidence of paraplegia after reperfusion of ischemic spinal cord in a rabbit model. (J Vasc Surg 1998;27:109-16.)

Bioluminescence mechanism on new systems

Abstract

Mobility of humic substances, major and minor elements in lake Skjervatjern and its catchment area

Water and soil water samples from the humic lake experimental site in western Norway (HUMEX) were fractionated according to size by use of a cross flow ultrafiltration technique, and analysed for dissolved organic carbon (DOC), major ions, and several trace elements (e.g., Al, Fe, Mn, Zn, La, Sm, and Sc). Results from sampling seasons with different hydrological flow regimes are compared. Samples were taken both within the acid treatment site (A) and the control site (B). In the lake water samples, the relative importance of the low molecular weight fraction (L-Mw; Mw<3kDa) compared to the medium molecular weight fraction (M-Mw; 3kDa<Mw<10kDa) of DOC, organically complexed Al (Al o), Fe, and Mn was higher during a low flow period (LF) in July 1992 than in a medium flow period (MF) in June 1991. This difference was most distinct for the basin treated with acid (A). The LF period had higher ionic strength and lower concentration of DOC than the MF period. During a high flow period (HF) in October 1992, the transport of DOC and trace elements (Fe, Mn, La, and Sm) associated with a high molecular weight fraction (H-Mw; Mw > 10kDa) of DOC increased. In the lake, the major fraction of Al o was present as H-Mw forms, showing small differences in June 1991 (MF) and July 1992 (LF). There seemed to be an increased mobilization of Al in the form of inorganic Al species (Al i) in July 1992 (LF) compared to June 1991 (MF), especially in Basin A (lower DOC, increased concentration of SO 4 2−. Al i was mainly at M-Mw and L-Mw forms. In the podzol profile, the relative importance of the L-Mw fraction seemed to increase with depth in June 1991 (MF) and July 1992 (LF), a size distribution pattern which also was observed in the dystric histosol in June 1991 (MF). This indicates that the vertical transport of L-Mw forms are higher than H-Mw forms.

Determination of Free and Bound Cd, Zn, Cu, and Ag Ions in Lobster (Homarus americanus) Digestive Gland Extracts by Gel Chromatography Followed by Atomic Absorption Spectrophotometry and Polarography

Abstract Gel-permeation chromatography followed by atomic absorption spectrophotometric and polarographic analyses were used to measure free and bound divalent metal ions in lobster digestive gland extracts prepared with or without oc-toluenesulfonyl fluoride, a protease inhibitor. Chromatography on Sephadex G-50 or G-100 yielded 3 UV-absorbing peaks, which corresponded, respectively, to the void volume, a medium molecular weight fraction, and a low molecular weight fraction that contained free divalent metal ions. In protease-inhibited extracts, only Zn+2 was found, whereas Cd, Cu, and Ag were bound in high and medium molecular weight fractions. Cd+2 and Zn+2 were rapidly released from their bound forms in the absence of a protease inhibitor, and their presence was confirmed by polarography with EDTA. Gel-permeation chromatography coupled with atomic absorption spectrophotometry offers a rapid method for following changes in the concentrations of bound and free metal ions during processing of shellfishbased foodstuffs.

Zinc absorption and transport from complete humate and high and medium molecular weight fractions

Absorption and transport of zinc were measured using sunflower plants cultured in nutrient solution with 65Zn as a tracer. Five different zinc sources were evaluated: ZnHA with complete humic acid; ZnHA medium, with medium molecular weight humic fraction; ZnHA high, with the high molecular weight humic fraction; Zn-EDTA and ZnCl 2. The plants were found to absorb more zinc from ZnHA medium than from the other sources, both after 48 and 96 h. Little difference was observed in the amount absorbed from the other sources. The relative importance of humic acids in the micronutrient intake of plants is discussed.

Edaphic mobility of complete humic acid and fractions of high and medium molecular weight

Soil mobility of a complete humic acid and high and medium molecular weight fractions was determined by a soil TLC method. High and medium molecular weight fractions were obtained by ultrafiltration and then labeled with radioiodine. Infrared, visible- and UV spectra, as well as isotachophoretic studies, showed marked differences among the three humic fractions. The results obtained made evident the presence of soil mobile humic fractions of medium molecular weight. Alkalinization increased the soil mobility of humic acid.

Fractionation, radioiodination and mobility in soil plates of different molecular weight fractions of humic acids

Humic acids were fractionated by ultrafiltration in high and medium molecular weight fractions and then labelled with I 131. Radiochemical yield was determined by paper chromatography and soil mobility by a TLC method. Differences between fractions were obtained, showing MMW higher values of radiochemical yield and soil mobility.

Preparation and characterization of model humic polymers containing organic phosphorus

The nature of organic P in soil organic matter was studied by evaluating the incorporation of serine, phosphoserine, ethanolamine, phosphoethanolamine and glycerophosphate into model humic polymers prepared by chemical oxidation of polyphenols. Elemental and functional group analysis indicated that the composition of model humic polymers ranged as follows: organic C, 50.6–56.8%; total acidity, 7.86–11.87m-equiv g −1; carboxyl, 1.42–2.00 m-equiv g −1; total hydroxyl, 6.79-10.0 m-equiv g −1; ash, 6.4–13.9%; E 4/E 6 ratio, 5.34–6.19; organic N, 0.70–1.65% and organic P, 0.254–0.942%. These values are within the ranges reported for soil humic substances. The only non-phenolic compounds incorporated into model humic polymers were those containing free amino groups. The P content of model polymers was not increased by the presence of KH 2PO 4, glycerophosphate, serine or ethanolamine whereas phosphoserine and phosphoethanolamine resulted in model polymers containing 0.254 and 0.942% P, respectively. Further characterization studies of the model polymer containing phosphoethanolamine (HA-PE) showed that most of the C (83.2%), N (79.8%) and P (75.3%) was in the humic acid fraction. Gel filtration of HA-PE showed that 0.5% of the polymer was present in high molecular weight (mol. wt) components (mol. wt > 100,000) and 74.8% of the polymer was in two components of mol. wt 10,000–50,000. The majority of the organic P in HA-PE was associated with the medium molecular weight fractions (79.2%) while 16.8% of the P was associated with materials possessing mol. wt < 10,000. Attempts to demonstrate the presence of organic P functional groups contained in HA-PE by infrared spectroscopy was limited by the relatively small amounts of organic P incorporated into the model humic polymers. The results obtained show that a portion of the unidentified organic P in soil humic substances may arise from the incorporation of organic compounds containing both amino and phosphate ester functional groups during oxidative polymerization of polyphenols.