High Molecular Weight Components Research Articles

Insight into the fenton-induced degradation process of extracellular polymeric substances (EPS) extracted from activated sludge

Although EPS in microbial aggregates are importance in successful implementation of biological wastewater treatment systems, they also exhibit detrimental role on certain circumstance, such as excess sludge dewatering. Extensive efforts have been put into the disruption of EPS for improving the dewaterability of excess sludge and Fenton's reagent treatment has been demonstrated to be a very promising sludge conditioning method for EPS destruction. However, the information regarding detailed degradation process of EPS during Fenton's reagent treatment is limited. In this study, EPS were extracted from activated sludge and treated with different concentrations of Fenton's reagent. The physicochemical characteristic changes of EPS under different treatment were investigated in terms of components, EEM, molecular weight (MW), UV-Vis and FTIR. The results showed that EPS were prone to be disintegrated, but hard to be fully mineralized. Humic substances in EPS were more resistant to Fenton's reagent than other components. Low MW components of EPS were preferentially degraded prior to the disruption of high MW components. Besides, the disintegration of EPS into lower MW ones was accompanied by the formation of higher MW compounds caused by the bridge interaction of Fe ions. The cleavage of protein's backbone in EPS was mainly through destruction of amide II (N–H and C–N) in –CO–NH–. Fenton's reagent treatment also led to a significant increase of oxygen-containing functional groups in EPS molecules. This paper may pave a path to deeply understand the mechanisms of dewatering improvements of excess sludge by Fenton's conditioning.

Rheological properties of asphalt binder modified with recycled asphalt materials and light-activated self-healing polymers

Ultraviolet (UV), light-activated, self-healing polymers are an emerging technology that was proposed to enhance the elastic behavior of asphalt binder, while improving its self-healing properties. The objective of this study was to evaluate the effects of self-healing polymer on the rheological properties of binder blends prepared with or without recycled asphalt materials. Binder blends were prepared with two different binders (PG 67-22 and PG 70-22M), with or without recycled asphalt materials, and 5% self-healing polymer (Oxetane-substituted Chitosan-Polyurethane). High-Pressure Gel Permeation Chromatography (HP-GPC) results showed an increase in High Molecular Weight (HMW) components in the binder with an increase in stiffness through the addition of recycled materials. A further increase was observed with the addition of self-healing polymer. Fourier Transform Infrared Spectroscopy (FTIR) confirmed High-Pressure Gel Permeation Chromatography (HP-GPC) results with an increase in the carbonyl index. Furthermore, the addition of recycled materials led to an increase in the high-temperature grade and the low-temperature grade of the binder blends, while the self-healing polymer did not have a significant effect on the PG-grade. Overall, the addition of self-healing polymer led to an increase in stiffness and an improvement in the rutting performance, while it did not have a positive effect on low-temperature cracking performance. For unmodified binder (PG 67-22), self-healing polymer incorporation improved the elastic and fatigue cracking properties of the binder. However, when it was added to a polymer-modified binder (PG 70-22M) and/or binder blends containing recycled asphalt materials, the potential of this material was low to negative on the low temperature and fatigue cracking performances.

Features of the change in the composition heavy oils of various types and solid asphaltite in the hydrothermal-catalytic conditions

The paper reveals the distinctive features of the change in the composition heavy oils of various types and of natural bitumen - asphaltite from the sandstones of the Permian sediments of the Spiridonovsky field in the territory of Tatarstan, in model experiments at a temperature of 250°C, characteristic for steam-thermal impact on the formation, and the pressure in the system of not more than 2 MPa. The choice of low pressure is due to the fact that bituminous rocks in the Permian sediments occur at relatively shallow depths in the near-surface deposits of the sedimentary strata, which necessitates the development of special technologies for their extraction. The experiments used natural iron oxide - hematite. As a part of the products of asphaltite conversion under the influence of hydrothermal-catalytic factors, the content of hydrocarbons almost 4-fold, the content of alcohol-benzene resins and asphaltenes decreases. The content of benzene resins increases somewhat. The composition of asphaltite proved to be less stable than of heavy oils from age-old sediments, apparently due to special conditions for the formation of its composition in natural conditions under the influence of secondary low-temperature biochemical processes that led to the accumulation of thermally unstable resinous-asphaltene components. Compared with the original asphaltite, in the products of the experiment, the content of alkanes of composition C10-C30 substantially increases with an obvious predominance of homologues with an even number of carbon atoms in the molecule. The product is characterized by a lesser degree of aromaticity and content of sulfoxide groups. The results of the studies showed the possibility of upgrading the composition of solid bitumen - asphaltite in in situ conversion by diluting its composition with lighter newly formed hydrocarbons, due to the destruction of its high molecular weight components.

Catalytic Conversion of Tatarstan Heavy Oil using Copper Based Catalysts at 250 °C

In this work, the in-situ upgrading of heavy oil from Tatarstan oilfield using steam and copper stearate as a catalyst at 250 °C and 35 bar for 24 hours was studied in stainless-steel reactor. Changes in the density/API gravity, viscosity, chemical composition (SARA-analysis), elemental composition and structure (FTIR-spectroscopy) of heavy oil before and after conversion were determined. Generally, we can summarize, that the content of resins and asphaltenes as well as the average molecular weight of heavy oil were reduced after conversion process. Whereas, amount of saturated and aromatic hydrocarbons was increased due to the destruction of its high molecular weight components. Also, irreversible decrease of viscosity was fixed.

Physical model experiment of heavy oil aquathermolysis with cobalt-iron based catalyst

Increasing steam-thermal methods efficiency for heavy using various catalysts is generating considerable interest in scientific research all over the world. Thus, it is worth to optimize catalyst effectiveness during their in-situ formation from oil soluble precursors using different transition metals. In this paper, a physical simulation of heavy oil catalytic aquathermolysis from the Ashalchinskoye field was carried out. The process was carried out in the presence of a hydrogen donor and a mixture of oil-soluble iron and cobalt metal tallate (1:1 weight ratio) at temperatures 250 °C and different exposure time (6 and 24 h). It was found that the most effective conditions for the thermal conversion of the oil under study are a temperature of 250 °C at 24 hours. In this case, a significant decrease in the proportion of high molecular weight components, mainly resins (by 39 %) and viscosity (about 45 %) occurs due to the course of destructive processes. At the same time, GCMS analysis of the aromatic oil fraction showed that an increase in time promotes the redistribution of mono- and polyaromatic structures.

Aquathermolysis of heavy oil in the presence of supercritical water

The purpose of the work is to identify patterns of transformation of high-molecular components of super-heavy oil by hydrothermal-catalytic processes, namely in the presence of a supercritical state of water. The regularities of changes of the component, structural-group, fractional and elemental compositions of heavy oil during the conversion under the above conditions were established, rheological characteristics of the initial crude oil and converted oil were studied as well. As a result of carrying out aquathermolysis in the supercritical water environment and in the presence of carbonaceous substances, the high-molecular weight components of the initial crude oil were degraded with the formation of light distillate fractions, which were scarcely present in the initial crude oil.

Infrared spectroscopic study of the coil-helix transition of highly concentrated gelatin formulations

The aim of this study was to investigate the applicability of ATR-FTIR spectroscopy as an analytical tool to monitor the gel formation of highly concentrated gelatin formulations. Spectral changes induced by the coil-helix transition have been studied and related to the elasticity parameter G′ obtained by oscillatory rheology in simultaneous measurements. A principal component analysis of the amide I band allowed the evaluation of triple helix formation kinetics. It was found that the key frequencies of the amide I band at 1657 and 1612 cm−1 represent the transition of the gelatin molecules from the random coil to the triple helical conformation in the emerging gel. A direct correlation between the conformation of the gelatin molecules and the gel elasticity was obtained for a commercially available pharmaceutical grade limed bone gelatin in concentrations between 20 and 40% w/w. The same was valid upon addition of small gelatin peptides or a helix inhibitor. No such correlation between triple helix content and G′ was found for limed bone gelatins of the same Bloom value but an asymmetric molecular weight distribution with extremely high fractions of high or low molecular weight components. This suggests that early gel elasticity is not solely linked to the triple helix nucleation. Hence, our results indicate that FTIR spectroscopy can be applied to gain a better understanding of the relationship between triple helix content and elastic gel properties of pharmaceutical gelatin capsule shell formulations.

Polarity and Molecular Weight of Compost-Derived Humic Acids Impact Bio-dechlorination of Pentachlorophenol.

Compost-derived humic acids (HAs) as cheap soil conditioners have potential to facilitate pentachlorophenol (PCP) bio-dechlorination but lack proof and studies. To clarify this, PCP bio-dechlorination mediated by compost-derived HAs under Fe(III) reduction conditions was investigated. Reverse phase high-performance liquid chromatography and high-performance size exclusion chromatography were employed to identify the functional components within compost-derived HAs. Our results showed that compost-derived HAs facilitated the bio-dechlorination of PCP under Fe(III) reduction conditions, and four kinds of byproducts were detected during the process. The relatively hydrophilic and high molecular weight (MW) components within compost-derived HAs presented significant associations with the concentration of byproducts from bio-dechlorination of PCP in Fe2O3 reduction conditions. In contrast, the hydrophobic and low MW components were the main functional components for PCP bio-dechlorination in Fe3O4 reduction environment. These findings clarified the effects of polarity and MW of compost-derived HAs on PCP bio-dechlorination, giving clues to optimize composting technology to utilize compost products for in situ contamination remediation of paddy soil.

Manufacture of high density carbon blocks by self-sintering coke produced via a two-stage heat treatment of coal tar

High-strength and high-density carbonized carbon blocks from self-sintering coke were manufactured using coal tar and two-stage heat treatments (1st and 2nd stage treatments). First, the molecular weight distribution of the refined coal tar was controlled through a pressured heat treatment (1st stage treatment). Second, the 1st stage heat-treated coal tar (1S-CT) was treated using a delayed coking system (2nd stage treatment) to become the self-sintering coke. Finally, carbon blocks were molded from 2nd stage heat-treated coke (2S-C) and carbonized at 1200 °C for 1 h. Through rapid decomposition of the high molecular weight components in the coal tar at 360 °C in the 1st stage treatment, the molecular weight distribution of coal tar was confirmed to be controllable by the 1st stage treatment. Swelling during carbonization was observed in carbon blocks manufactured from 2S-C containing more than 15 wt% of volatile matter from 150–450 °C. The optimum conditions of the two-stage heat treatments were confirmed to be 300 °C for 3 h and 500 °C for 1 h. The highest density and flexural strength of the carbonized carbon blocks manufactured from 2S-C were 1.46 g/cm3 and 69.2 MPa, respectively.

Deterioration of oil quality during sample storage: Are stored reservoir core samples a viable resource for oil viscosity determination?

The physical and chemical properties of oil residing in reservoir core samples are strongly susceptible to evaporative processes during storage. In a case study from the Peace River oil sands of Alberta, we performed dead oil viscosity measurements on oils recovered by mechanical extraction of fresh core, the equivalent cores stored for 7 months frozen plus 3 months at ambient conditions (time 1) and for 7 months frozen plus 8 months at ambient conditions (time 2). The dead oil viscosity of oil recovered from fresh core material (8100 cP at 20 °C) was more than an order of magnitude lower than that of the oil subsequently recovered from an equivalent core sample stored frozen for 7 months and then at ambient temperature for 8 months (313,500 cP at 20 °C). The evaporation of light hydrocarbons such as toluene and xylenes during storage is a continuous process responsible for progressive increase in dead oil viscosity. Meanwhile, when comparing the oils recovered from fresh core and aged core samples, the composition of the heavy (low volatility) hydrocarbons remains essentially the same. Because biodegradation is the primary control on oil viscosity and variation in hydrocarbon compositions for this oil sample suite, partial least squares models based on viscosity versus geochemical data may still be used to predict viscosity. Although the physical properties of the oil may be compromised during storage, the distributions of the high molecular weight components retain characteristics, similar to a bar code, that are inherited and representative of the original (fresh) core sample. Therefore, with the proviso that the distributions of high molecular weight components are comparable between fresh cores and aged cores, the viscosity of oil residing in stored core samples can be effectively restored by chemometric-based correlation methods.

Preparation and Characterization of Gelatin and Antioxidant Peptides from Gelatin Hydrolysate of Skipjack Tuna (Katsuwonus pelamis) Bone Stimulated by in vitro Gastrointestinal Digestion.

In China, a large amount of fish bones are produced during the processing of tuna cans production. For full use of those by-products, gelatin (STB-G) with a yield of 6.37 ± 0.64% was extracted from skipjack tuna (Katsuwonus pelamis) bone using water at 60 °C for 8 h. Amino acid analysis showed that STB-G contained Gly (340.3 residues/1000 residues) as the major amino acid and its imino acid content was 177.3 residues/1000 residues. Amino acid composition, SDS-PAGE, and Fourier transform infrared (FTIR) spectrum investigations confirmed that the physicochemical properties of STB-G were similar to those of type I collagen from skipjack tuna bone (STB-C), but partial high molecular weight components of STB-G were degraded during the extraction process, which induced that the gelatin was easier to be hydrolyzed by protease than mammalian gelatins and was suitable for preparation of hydrolysate. Therefore, STB-G was hydrolyzed under in vitro gastrointestinal digestion (pepsin-trypsin system) and five antioxidant peptides were purified from the resulted hydrolysate (STB-GH) and identified as GPDGR, GADIVA, GAPGPQMV, AGPK, and GAEGFIF, respectively. Among the gelatin hydrolysate, fractions, and isolated peptides, GADIVA and GAEGFIF exhibited the strongest scavenging activities on 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical (EC50 0.57 and 0.30 mg/mL), hydroxyl radical (EC50 0.25 and 0.32 mg/mL), superoxide anion radical (EC50 0.52 and 0.48 mg/mL), and 2,2′-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) radical (EC50 0.41 and 0.21 mg/mL). Moreover, GADIVA and GAEGFIF showed a high inhibiting ability on lipid peroxidation in a linoleic acid model system. The strong activities of five isolated peptides profited by their small molecular sizes and the antioxidant amino acid residues in their sequences. These results suggested that five isolated peptides (STP1–STP5), especially GADIVA and GAEGFIF, might serve as potential antioxidants applied in health food industries.

Dynamic changes in optical and chemical properties of tar ball aerosols by atmospheric photochemical aging

Abstract. Following wood pyrolysis, tar ball aerosols were laboratory generated from wood tar separated into polar and nonpolar phases. Chemical information of fresh tar balls was obtained from a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) and single-particle laser desorption/resonance enhanced multiphoton ionization mass spectrometry (SP-LD-REMPI-MS). Their continuous refractive index (RI) between 365 and 425 nm was retrieved using a broadband cavity enhanced spectroscopy (BBCES). Dynamic changes in the optical and chemical properties for the nonpolar tar ball aerosols in NOx-dependent photochemical process were investigated in an oxidation flow reactor (OFR). Distinct differences in the chemical composition of the fresh polar and nonpolar tar aerosols were identified. Nonpolar tar aerosols contain predominantly high-molecular weight unsubstituted and alkyl-substituted polycylic aromatic hydrocarbons (PAHs), while polar tar aerosols consist of a high number of oxidized aromatic substances (e.g., methoxy-phenols, benzenediol) with higher O : C ratios and carbon oxidation states. Fresh tar balls have light absorption characteristics similar to atmospheric brown carbon (BrC) aerosol with higher absorption efficiency towards the UV wavelengths. The average retrieved RI is 1.661+0.020i and 1.635+0.003i for the nonpolar and polar tar aerosols, respectively, with an absorption Ångström exponent (AAE) between 5.7 and 7.8 in the detected wavelength range. The RI fits a volume mixing rule for internally mixed nonpolar/polar tar balls. The RI of the tar ball aerosols decreased with increasing wavelength under photochemical oxidation. Photolysis by UV light (254 nm), without strong oxidants in the system, slightly decreased the RI and increased the oxidation state of the tar balls. Oxidation under varying OH exposure levels and in the absence of NOx diminished the absorption (bleaching) and increased the O : C ratio of the tar balls. The photobleaching via OH radical initiated oxidation is mainly attributed to decomposition of chromophoric aromatics, nitrogen-containing organics, and high-molecular weight components in the aged particles. Photolysis of nitrous oxide (N2O) was used to simulate NOx-dependent photochemical aging of tar balls in the OFR. Under high-NOx conditions with similar OH exposure, photochemical aging led to the formation of organic nitrates, and increased both oxidation degree and light absorption for the aged tar ball aerosols. These observations suggest that secondary organic nitrate formation counteracts the bleaching by OH radical photooxidation to eventually regain some absorption of the aged tar ball aerosols. The atmospheric implication and climate effects from tar balls upon various oxidation processes are briefly discussed.

Thermal Stability of High Density Polyethylene-Clay Nanocomposites Produced by in situ Solvent Polymerization

High density polyethylene and high density polyethylene-clay nanocomposites were produced using direct solvent polymerization and a Ziegler catalyst system (TiCl4 and triethylaluminum in hexane). The produced polymer has a high average molecular weight and a multimodal molecular weight distribution composed of four distributions including a very high molecular weight component. The laboratory polymer has a thermal stability in inert atmosphere similar to the commercial high density polyethylene produced by Braskem. In oxidant atmosphere the produced polymer presents three thermal oxidation events above 400ºC due to the combustion of low, medium and high molecular weight molecules. The thermal oxidation of the nanocomposites is shifted and reduced for high temperatures indicating an improvement in the thermal stability of the polymeric matrix due to the clay barrier effect for gases and volatile compounds.

Моделирование изменения компонентного состава в залежах со значительным этажом продуктивности и градиентом температуры

This paper compares three methods for calculation of initial composition variation with depth in hydrocarbon reservoirs: considering thermal diffusion, considering temperature gradient without thermal diffusion effects; and by gravity forces only. Newton method-based numerical algorithm was implemented for solution of thermodynamic equations to evaluate pressure and hydrocarbon composition. Test calculations are performed for main gas-condensate reservoir of Vuktylskoye field with a gas column of 1350 m. The results obtained with the numerical algorithm indicate that gravity segregation impact is the strongest for all the cases considered. Concentration decreases with depth for low molecular weight components and increases for high molecular weight components. The higher molecular weight of the component, the stronger variation of its concentration with depth. Initial reservoir pressure also changes accordingly. However, thermal diffusion also has a significant influence on variation of hydrocarbon composition with depth and initial reservoir pressure. For the test case considered, thermal diffusion magnifies the impact of gravity and results in strongly nonlinear dependencies of component concentrations on depth. When thermal gradient is taken into account without thermal diffusion effects, the results are only slightly different from those with the isothermal gravity segregation calculations. None of the calculation methods were successful in matching estimates of initial composition variation with depth obtained from well exploitation data. Physical mechanisms governing variation of composition within the main reservoir of the Vuktylskoye field require additional investigation. Despite the long history of the reservoir development, this problem was previously studied based only on field development data.

Surface and aggregation properties of a plant-oil derived biosurfactant

The plant-oil derived biosurfactant HeBra® shows a high surface activity combined with a versatile aggregation behavior. The hydrophilic protein head groups provide an excellent water solubility that still enables micelle formation due to the hydrophobic interactions of the fatty acid chains. The observed low CMC of 1 g L-1 allows an efficient utilization in different application fields already at very low concentrations. The mixture of low and high molecular weight components provides highly dynamic behavior during foam formation or dispersion processes combined with the formation of large and stable structures in solutions and at surfaces.

Effects of Polyethylene Molecular Weight Distribution on Phase Morphology Development in Poly(p-phenylene ether) and Polyethylene Blends

Bimodal molecular weight distribution (MWD) in a polymer can potentially deliver mechanical toughness from the high molecular weight (MW) components without compromising its processability due to the presence of the low MW components. The influence of MW bimodality on the morphology development in a heterophase polymer blend system, however, remains unclear. In this study, high-density polyethylenes (HDPEs) of high unimodal, low unimodal, and bimodal MWDs, namely HDPE-H, HDPE-L, and HDPE-B, were synthesized and then blended with PPE to study the effect of the MWD on morphology development. After blending, the low MW components in HDPE-B are found to populate the HDPE/PPE interface, and the morphological and continuity behaviors of PPE in HDPE-B/PPE are virtually identical to those in the unimodal HDPE-L/PPE blend. Despite the high interfacial tension between HDPE and PPE, all three HDPEs form fiber-like dispersions in HDPE/PPE blends when PPE is the majority phase. This leads to an early HDPE phase contin...

Aquathermolysis of heavy oil in reservoir conditions with the use of oil-soluble catalysts: part I – changes in composition of saturated hydrocarbons

This paper is devoted to the study of aquathermolysis processes of heavy oil produced by CSS technology on Boca de Jaruco oil field. Various catalysts based on cobalt, nickel, iron and copper were used for intensification of in-situ upgrading processes of heavy oil. The first paper in series is presented results of transformation of crude oil and its saturate fraction after thermal treatment with and without catalysts by SARA analysis, MALDI mass-spectrometry, FTIR-spectroscopy and gas chromatography. It is revealed, that catalysts provide more deep conversion of asphaltenes and resins into lighter hydrocarbons. Particularly, for the given heavy oil, catalysts based on iron and nickel organic salts are more effective to reduce the content of high molecular weight components (asphaltenes). Saturates fraction after thermal treatment in presence of the catalysts is enriched with lighter alkanes in comparison to the crude oil treated without catalysts. Obtained results show that crude oil recovered by catalytic aquathermolysis processes will be better quality than the original oil in the place.

Shear induced crystallization of bimodal and unimodal high density polyethylene

In-situ step-shear experiments by synchrotron X-ray techniques were performed to study shear-induced crystallization of bimodal (BM1) and unimodal (UM1) high-density polyethylene (HDPE). The BM1 sample consisted of a bimodal molecular weight (MW) and composition distribution with the low MW components having less short chain branches (SCBs), or hexene co-monomer, and the high MW components having more SCBs. The average molecular weight of BM1 was higher than that of UM1, where both BM1 and UM1 covered the same molecular weight range. The UM1 sample contained a unimodal but broad molecular weight distribution (MWD) with a constant SCB value between those of the low and high MW components in BM1. Discrete primary and secondary lamellae were found in BM1 and UM1, whereas UM1 exhibited faster secondary lamellar growth. Shear-induced crystallization resulted in higher lamellar orientation in UM1, but higher crystallinity in BM1. The large fraction of medium high MW components in UM1 was found to be effective in crystallization under deformation, leading to stronger shear-induced crystalline orientation.

Environmental petroleum pollution analysis using ramped pyrolysis-gas chromatography–mass spectrometry

In response to the Deepwater Horizon oil spill, critical research has tracked the changes in petroleum hydrocarbons with environmental weathering. There are limitations, however, whereby single analytical techniques cannot always identify the wide breadth of petroleum and petroleum-derived compounds. We explore the analytical capabilities of ramped pyrolysis-gas chromatography–mass spectrometry (Py-GC–MS) to evaluate environmental samples of petroleum hydrocarbons from the Deepwater Horizon oil spill. We show that bulk flow Py-GC–MS can quantify the overall degree of petroleum hydrocarbon weathering. Furthermore, thermal slicing Py-GC–MS can quantify specific compounds in the “thermal desorption zone” (50–370 °C), as well as characterize pyrolyzed fragments from non-GC-amenable petroleum hydrocarbons (including oxygenated hydrocarbons) in the “cracking zone” (370–650 °C). Our data also suggest an increase in thermochemical stability, concentration of oxygenated products and complexity of high molecular weight and/or polar components with advanced weathering. This analysis not only elucidates weathering trends in Deepwater Horizon oil over several years, but also illustrates the analytical capacity of this method for future petroleum hydrocarbon investigations, filling a void in research connecting Py-GC–MS and environmentally weathered oil samples.

Impact of PEGylation on the mucolytic activity of recombinant human deoxyribonuclease I in cystic fibrosis sputum.

Highly viscous mucus and its impaired clearance characterize the lungs of patients with cystic fibrosis (CF). Pulmonary secretions of patients with CF display increased concentrations of high molecular weight components such as DNA and actin. Recombinant human deoxyribonuclease I (rhDNase) delivered by inhalation cleaves DNA filaments contained in respiratory secretions and thins them. However, rapid clearance of rhDNase from the lungs implies a daily administration and thereby a high therapy burden and a reduced patient compliance. A PEGylated version of rhDNase could sustain the presence of the protein within the lungs and reduce its administration frequency. Here, we evaluated the enzymatic activity of rhDNase conjugated to a two-arm 40 kDa polyethylene glycol (PEG40) in CF sputa. Rheology data indicated that both rhDNase and PEG40-rhDNase presented similar mucolytic activity in CF sputa, independently of the purulence of the sputum samples as well as of their DNA, actin and ions contents. The macroscopic appearance of the samples correlated with the DNA content of the sputa: the more purulent the sample, the higher the DNA concentration. Finally, quantification of the enzymes in CF sputa following rheology measurement suggests that PEGylation largely increases the stability of rhDNase in CF respiratory secretions, since 24-fold more PEG40-rhDNase than rhDNase was recovered from the samples. The present results are considered positive and provide support to the continuation of the research on a long acting version of rhDNase to treat CF lung disease.