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  • 1. Andersson, M.
    et al.
    Wittgren, B.
    Schagerlof, H.
    Momcilovic, Dane
    Wahlund, K. G.
    Size and structure characterization of ethylhydroxyethyl cellulose by the combination of field-flow fractionation with other techniques. Investigation of ultralarge components2004Ingår i: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 5, nr 1, s. 97-105Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ethylhydroxyethyl cellulose (EHEC) of three different viscosity classes (EHEC I, II, and III) was analyzed by programmed cross-flow asymmetrical flow field-flow fractionation coupled to multiangle light scattering and refractive index detectors to determine their size and molar mass distribution. Two size populations were detected in the two lower viscosity classes, EHEC I and II, one high molar mass and one ultrahigh molar mass (UHM). The two covered molar masses from 10(4) up to 10(9) g.mol(-1). The highest viscosity class EHEC III was less size-dispersed covering molar masses from 5x10(5) to 5x10(7) g.mol(-1). Filtering of the EHEC II solution removed small amounts of compact UHM material. Enzyme treatments were performed on EHEC II to further characterize it. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and anion ion-exchange chromatography coupled to pulsed amperometric detection showed that the UHM component contained EHEC.

  • 2.
    Enebro, Jonas
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Momcilovic, Dane
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Siika-Aho, Matti
    VTT Technical Research Centre of Finland, Espoo.
    Karlsson, Sigbritt
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    A New Approach for Studying Correlations between the Chemical Structure and the Rheological Properties in Carboxymethyl Cellulose2007Ingår i: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 8, nr 10, s. 3253-3257Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Two model sodium carboxymethyl celluloses (CMC) with similar monomer composition but with significant differences in the viscoelastic properties, that could not be assigned to variations in the average molar mass or molar mass distribution, were investigated with respect to the fraction of nonsubstituted cellulose segments in the polymers. The CMCs were hydrolyzed by a purified highly selective endoglucanase. The average molar mass and molar mass distribution of the enzyme products, as measured by size-exclusion chromatography with online multi-angle light scattering and refractive index detection (SEC/MALS/RI), revealed that the enzyme-catalyzed hydrolysis was more effective on one of the CMCs. To investigate whether this was due to a higher fraction of nonsubstituted cellulose segments in the polymer, the concentrations of nonsubstituted enzyme products, e.g., cellotetraose and cellopentaose, were measured by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS). It was concluded that the two CMCs displayed significant differences in the fraction of nonsubstituted cellulose segments. Furthermore, the CMC with the strongest attractive intermolecular interactions, according to rheometry, also contained the highest fraction of nonsubstituted cellulose segments.

  • 3.
    Enebro, Jonas
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Momcilovic, Dane
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Siika-Aho, Matti
    VTT Technical Research Center of Finland, Espoo.
    Karlsson, Sigbritt
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Investigation of endoglucanase selectivity on carboxymethyl cellulose by mass spectrometric techniques2009Ingår i: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 16, nr 2, s. 271-280Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The benefits of applying cellulose selective enzymes as analytical tools for chemical structure characterization of cellulose derivatives have been frequently addressed over the years. In a recent study the high selectivity of cellulase Cel45A from Trichoderma reesei (Tr Cel45A) was utilized for relating the chemical structure to the flow properties of carboxymethyl cellulose (CMC). However, in order to take full advantage of the enzymatic hydrolysis the enzyme selectivity on the cellulose substrate must be further investigated. Therefore, the selectivity of Tr Cel45A on CMC was studied by chemical sample preparation of the enzyme products followed by mass spectrometric chemical structure characterization. The results strongly suggest that, in accordance with recent studies, also this highly selective endoglucanase is able to catalyze hydrolysis of glucosidic bonds adjacent to mono-substituted anhydroglucose units (AGUs). Furthermore, the results also indicate that substituents on the nearby AGUs will affect the hydrolysis.

  • 4.
    Enebro, Jonas
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Momcilovic, Dane
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Siika-Aho, Matti
    VTT Technical Research Centre of Finland, Espoo.
    Karlsson, Sigbritt
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Liquid Chromatography combined with Mass Spectrometry for the Investigation of Endoglucanase Selectivity on Carboxymethyl Cellulose2009Ingår i: Carbohydrate Research, ISSN 0008-6215, E-ISSN 1873-426X, Vol. 344, nr 16, s. 2173-2181Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Endoglucanases are useful tools in the chemical structure analysis of cellulose derivatives. However, knowledge on the endoglucanase selectivity, which is of central importance for data interpretation, is still limited. In this study, new reverse-phase liquid chromatography mass spectrometry (LC-MS) methods were developed to investigate the selectivity of the endoglucanases Cel5A, cel7B, Cel45A, and Cel74A from the filamentous fungus Trichoderma reesei. The aim was to improve the identification of the regioisomers in the complex mixtures that are obtained after enzymatic hydrolysis. Reduction followed by per-O-methylation was performed in order to improve the separation in reverse-phase LC, increase MS sensitivity, and to facilitate structure analysis by MS/MS of O-carboxymethyl glucose and cellooligosaccharides. The cellulose selective enzymes that were investigated displayed interesting differences in enzyme selectivity on CMC substrates.

  • 5.
    Kaali, Peter
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Momcilovic, Dane
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Markstrom, Agneta
    Aune, Ragnhild E.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Czel, Gyorgy
    Karlsson, Sigbritt
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Degradation of Biomedical Polydimethylsiloxanes During Exposure to In Vivo Biofilm Environment Monitored by FE-SEM, ATR-FTIR, and MALDI-TOF MS2010Ingår i: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 115, nr 2, s. 802-810Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Polymers used for biomedical purposes in medical devices are usually requested to be inert to degradation. This article describes that slow irreversible changes were observed in silicone surfaces exposed to in vivo biofilms even if silicone, in general, is supposed to have excellent long-term properties. Tracheostomy tubes made of silicone rubber were exposed to in vivo biofilm environments in clinical tests for periods of 7, 3, and 6 months. The chemical degradation was monitored by MALDI-TOF MS, ATR-FTI.R, and FE-SEM. In addition, the physical changes were monitored by contact angle and hardness measurements. Cyclic polydimethylsiloxane (PDMS) was detected on the surfaces of new (unaged) silicones. On the surfaces of the in vivo samples new compounds, presumably linear methyl-hydroxyl-terminated PDMS, were detected in addition to cyclic PDMS. These compounds may be formed as a result of the hydrolysis of linear dimethyl terminated PDMS, which is also present in the silicone rubber. ATR-FTIR spectroscopy confirmed that hydrolysis had indeed occurred during the in vivo exposure, since Si-OH groups were detected. Furthermore, significant changes in the topography were detected by FE-SEM, indicating the initiation of degradation. No significant changes in the contact angle of the in vivo used samples were observed, but this information may be shielded by the fact that biofilm may remain on the surface, despite the thorough cleaning before the analysis. It is also possible that the surface hydrophobicity was recovered by the diffusion of linear low-molecular-weight compounds from the bulk.

  • 6.
    Kaali, Peter
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Strömberg, Emma
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Aune, Ragnhild E.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Czel, Gyoergy
    Department of Polymer Engineering, University of Miskolc.
    Momcilovic, Dane
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Karlsson, Sigbritt
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Antimicrobial properties of Ag+ loaded zeolite polyester polyurethane and silicone rubber and long-term properties after exposure to in-vitro ageing2010Ingår i: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 95, nr 9, s. 1456-1465Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In biomedical applications, tubes (e.g. catheters etc.) are commonly produced from polyurethane (PU) and silicone rubber which are known to be biocompatible materials. Several studies have shown that tubes, which are connected to the body (invasive) (especially urinary, tracheotomy and central venous catheters) are associated with infections. The present study reports the development of a new method aiming at obtaining antibacterial properties for PU and silicone rubber by mixing respective material with a natural antibacterial agent (Ag+ loaded zeolite) in different weight fractions. The influence of the zeolite content on the antimicrobial properties were analysed by exposure to bacteria (ISO 22196) and mixtures of fungi (ISO 846). The materials were also subject to artificial body fluids (Artificial Lysosomal Fluid (ALF) and Gamble's solution) for periods up to three months and the subsequent changes in the chemical properties after in-vitro exposure were determined by Matrix Assisted Laser Deposition/Ionization Time Of Flight Mass Spectrometry (MALDI-TOF MS) and Attenuated Total Reflection Fourier Transform Infra Red spectroscopy (ATR-FTIR). It was established that the antimicrobial effect of the materials increased with the increase of the zeolite content. The wettability of the materials was found to decrease significantly during the in-vitro exposure, but this could not be correlated to the zeolite content. In the PU samples, the formation of free carbonyl and -OH groups was observed, which corresponds to oxidative degradation. In case of the silicone rubber the ratio of cyclic PDMS to linear PDMS (H, CH3 and dimethyl terminated) decreased, which indicates a change in the concentration of the compounds. The formation and increase of the O-H bond during the exposure was also confirmed by the infrared spectra of the material which corresponds to hydrolysis of the silicone rubber.

  • 7. Karlsson, J.
    et al.
    Momcilovic, Dane
    Wittgren, B.
    Schulein, M.
    Tjerneld, F.
    Brinkmalm, G.
    Enzymatic degradation of carboxymethyl cellulose hydrolyzed by the endoglucanases Cel5A, Cel7B, and Cel45A from Humicola insolens and Cel7B, Cel12A and Cel45Acore from Trichoderma reesei2002Ingår i: Biopolymers, ISSN 0006-3525, E-ISSN 1097-0282, Vol. 63, nr 1, s. 32-40Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Enzymatic hydrolysis of carboxymethyl cellulose (CMC) has been studied with purified endoglucanases Hi Cel5A (EG II), Hi Cel7B (EG I), and Hi Cel45A (EG V)from Humicola insolens, and Tr Cel7B (EG I), Tr Cel12A (EG III), and Tr Cel45Acore (EG V)from Trichoderma reesei. The CMC, with a degree of substitution (DS) of 0.7, was hydrolyzed with a single enzyme until no further hydrolysis was observed. The hydrolysates were analyzed for production of substituted and non substituted oligosaccharides with size exclusion chromatographly (SEC) and with matrix-assisted laser desorption/ionization mass spectrometry (MALDI-TOF-MS). Production of reducing ends and of nonsubstituted oligosaccharides was determined as well. The two most effective endoglucanases for CMC hydrolysis were Hi Cel5.A and Tr Cel7B. These enzymes degraded CMC to lower molar mass fragments compared with the other endoglucanases. The products had the highest DS determined by MALDI-TOF-MS. Thus, Hi Cel5A and Tr Cel7B were less inhibited by the substituents than the other endoglucanases. The endoglucanase with clearly the lowest activity on CMC was Tr Cel45Acore. It produced less than half of the amount of reducing ends compared to Tr Cel7B; furthermore, the products had significantly lower DS. By MALDI-TOF-MS, oligosaccharide with different degree of polymerization (DP) and with different number of substituents could be separated and identified. The average oligosaccharide DS as function of DP could be measured for each enzyme after hydrolysis. The combination of techniques for analysis of product formation gave information on average length of unsubstituted blocks of CMC.

  • 8.
    Karlsson, Sigbritt
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Momcilovic, Dane
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Enebro, Jonas
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Cellulose and cellulose derivatives in biomedical materials: Tools to propose the chemical structure by mass spectrometry2009Ingår i: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 237Artikel i tidskrift (Övrigt vetenskapligt)
  • 9. Melander, C.
    et al.
    Momcilovic, Dane
    Nilsson, C.
    Bengtsson, M.
    Schagerlof, H.
    Tjerneld, F.
    Laurell, T.
    Reimann, C. T.
    Gorton, L.
    Microchip immobilized enzyme reactors for hydrolysis of methyl cellulose2005Ingår i: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 77, nr 10, s. 3284-3291Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Microchip immobilized enzyme reactors (mu IMERs) with immobilized endoglucanases were applied for the hydrolysis of methyl cellulose (MC). MCs of various molecular weights were hydrolyzed using two mu IMERs containing immobilized celloendoglucanase Cel 5A from Bacillus agaradhaerens (BaCel 5A) connected in series. Hydrolysis by the mu IMER could be confirmed from the average molar masses and molar mass distributions measured by size exclusion chromatography (SEC) with online multiangle light scattering and refractive index detection. Methylated cellooligosaccharides with degrees of polymerization (DP) between 1 and 6 formed during hydrolysis were analyzed by direct infusion electrospray ionization ion-trap mass spectrometry (ESI-ITMS). Mass spectra of mu IMER- and batch-hydrolyzed samples were compared and no significant differences were found, indicating that mu IMER hydrolysis was as efficient as conventional batch hydrolysis. A fast and automated hydrolysis with online MS detection was achieved by connecting the mu IMER to high-performance liquid chromatography and ESI-ITMS. This online separation reduced the relative intensities of interfering signals and increased the signal-to-noise ratios in MS. The mu IMER hydrolysates were also subjected to SEC interfaced with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. With this technique, oligomers with DP 3-30 could be detected. The hydrolysis by they mu-IMER was performed within 60 min, i.e. significantly faster compared with batch hydrolysis usually performed for at least 24 h. The mu IMER also allowed hydrolysis after 10 days of continuous use. The method presented in this work offers new approaches for the analysis of derivatized cellulose and provides the possibility of convenient online, fast, and more versatile analysis compared with the traditional batch method.

  • 10.
    Mischnick, Petra
    et al.
    Technische Universität Braunschweig, Institute of Food Chemistry.
    Momcilovic, Dane
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Chemical Structure Analysis of Starch and Cellulose Derivatives2010Ingår i: Advances in Carbohydrate Chemistry and Biochemistry, ISSN 0065-2318, E-ISSN 2162-5530, Vol. 64, s. 117-210Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    Starch and cellulose are the most abundant and important representatives of renewable biomass. Since the mid-19th century their properties have been changed by chemical modification for commerical and scientific purposes, and there substituted polymors have found a wide range of aplications. However, the inherent polydispersity and supramolecular organization of starch and cellulose cause the products resulting from their modification to display high complexity. Chemical composition analysis of these mixtures is therefore a challenging task. Detailed knowledge on substitution patterns is fundamental for understanding structure-property relationships in modified cellulose and starch, and thus also for the improvement of reproducibility and rational design of properties.Substitution patterns resulting from kinetically or thermodynamically controlled reactions show certain preferences for the three available hydroxyl functions in (1→4)-linked glucans. Spurlin, seventy years ago, was the first to describe this in an idealized model, and nowadays this model has been extended and related to the next hierarchical levels, namely, the substituent distribution in and over the polymer chains. This structural complexity, with its implications for data interpretation, and the analytical approaches developed for its investigation are outlined in this article. Strategies and methods for the determination of the average degree of substitution (DS), monomer composition, and substitution patterns at the polymer level are presented and discussed with respect to their limitations and interpretability. Nuclear magnetic resonance spectroscopy, chromatography, capillary electrophoresis, and modern mass spectrometry (MS), including tandem MS, are the main instrumental techniques employed, in combination with appropriate sample preparation by chemical and enzymatic methods.

  • 11. Momcilovic, Dane
    et al.
    Schagerlof, H.
    Rome, D.
    Jornten-Karlsson, M.
    Karlsson, K. E.
    Wittgren, B.
    Tjerneld, F.
    Wahlund, K. G.
    Brinkmalm, G.
    Derivatization using dimethylamine for tandem mass spectrometric structure analysis of enzymatically and acidically depolymerized methyl cellulose2005Ingår i: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 77, nr 9, s. 2948-2959Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Structure analysis of partially depolymerized methyl cellulose was performed by nanoelectrospray ionization tandem mass spectrometry (nano-ESI-MS/MS) and by matrix-assisted laser desorption/ionization tandem mass spectrometry (MALDI-MS/MS). Dimethylamine (DMA) was used for the first time as a reducing end derivatization reagent for oligosaccharides. This is an attractive reagent since it could be easily removed from the reaction mixture. Most important it also introduces a basic functional group that increased the sensitivity in both MALDI and nano-ESI. Depolymerization was made in two ways: one by the cellulose selective endoglucanase 5A from Bacillus agaradhaerens (Ba Ce15A) and the other by trifluoroacetic acid. The DMA derivatives formed both protonated and sodiated molecules in nano-ESI and MALDI. Tandem MS of protonated molecules yielded predominantly Y fragments from which the distribution of the substituents in the oligomers could be measured. Fragments obtained in tandem MS of sodiated molecules provided information regarding the positions of the substituents within the anhydroglucose units (AGUs). It was found that Ba Ce15A could cleave glucosidic bonds also if the AGU on the reducing side of the bond was fully methylated. The combination of DMA derivatization and tandem MS was demonstrated as a tool for the characterization of endoglucanase selectivity.

  • 12. Momcilovic, Dane
    et al.
    Schagerlof, H.
    Wittgren, B.
    Wahlund, K. G.
    Brinkmalm, G.
    Improved chemical analysis of cellulose ethers using dialkylamine derivatization and mass spectrometry2005Ingår i: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 6, nr 5, s. 2793-2799Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Oligosaccharides of hydroxypropylmethyl cellulose, hydroxypropyl cellulose, and methyl cellulose were investigated by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). The cellulose ether oligosaccharides were produced either by enzymatic depolymerization utilizing the purified family 5 endoglucanase from Bacillus agaradhaerens or by partial acidic depolymerization. To lower the limit of detection in MALDI-MS three dilakylamines, dimethyl-, diethyl-, and dipropylamine were studied as reagents for reductive amination of the oligosaccharides. All three amines contributed to a significant increase in sensitivity in MALDI-MS, especially for oligosaccharides with a degree of polymerization (DP) < 3. These reagents were also attractive due to their high volatility, which facilitated the purification of the reaction mixtures. It was established that low-mass discrimination in MALDI-MS in the DP range 1-7 was substantially reduced with dialkylamine derivatization. Hence, dialkylamine derivatization of cellulose ether oligosaccharides obtained by endoglucanase depolymerization increased the number of detected analyte components. Dimethylamine was concluded to be the preferred reagent of those evaluated.

  • 13. Momcilovic, Dane
    et al.
    Wahlund, K. G.
    Wittgren, B.
    Brinkmalm, G.
    Improved matrix-assisted laser desorption/ionisation sample preparation of a partially depolymerised cellulose derivative by continuous spray deposition and interfacing with size-exclusion chromatography2005Ingår i: Rapid Communications in Mass Spectrometry, ISSN 0951-4198, E-ISSN 1097-0231, Vol. 19, nr 7, s. 947-954Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Continuous spray deposition (CSD) of aqueous solutions of partially depolymerised methyl cellulose was found to improve matrix-assisted laser desorption/ionisation (MALDI) sample preparation. One feature was that the sensitivity in MALDI time-of-flight mass spectrometry increased up to an order of magnitude compared with the standard sample preparation method. Another feature was that CSD provided targets for MALDI with homogeneously distributed analyte. This resulted in a more even signal intensity and a higher reproducibility than in the standard method. High-mass discrimination was more pronounced in CSD than in the standard method. Size-exclusion chromatography with aqueous eluent was coupled online to CSD onto matrix-precoated foils. The suitability for determination of the molar mass distribution of methyl cellulose was investigated.

  • 14. Momcilovic, Dane
    et al.
    Wittgren, B.
    Wahlund, K. G.
    Karlsson, J.
    Brinkmalm, G.
    Sample preparation effects in matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry of partially depolymerised carboxymethyl cellulose2003Ingår i: Rapid Communications in Mass Spectrometry, ISSN 0951-4198, E-ISSN 1097-0231, Vol. 17, nr 11, s. 1107-1115Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Sample preparation effects in matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOFMS) of partially depolymerised carboxymethyl cellulose (CMC) have been investigated. The depolymerisation was either enzymatic or acidic. Fractions of enzymatically depolymerised CMC were collected from size-exclusion chromatography (SEC) and further investigated by MALDI-TOFMS. 2,5-Dihydroxybenzoic acid was used as matrix, dissolved in H2O due to the poor solubility of CMC in suitable organic solvents. The samples were dried by two methods, in ambient atmosphere and at reduced pressure. Under reduced pressure the sample spot homogeneity increased. This drying method, however, produced additional adduct peaks in the mass spectra originating from ion exchange on the CMC oligomers. Analysis of CMC could be performed in both negative and positive ion modes. Mass discrimination and variation in ionisation efficiency were demonstrated by comparing mass spectra with SEC data. Measurements of the degree of substitution (DS) were performed on three CMCs with different DS values, which were depolymerised in trifluoroacetic acid. The three CMCs were easily distinguished from one another, but the obtained DS values deviated from the values supplied by the manufacturer.

  • 15. Momcilovic, Dane
    et al.
    Wittgren, B.
    Wahlund, K. G.
    Karlsson, J.
    Brinkmalm, G.
    Sample preparation effects in matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry of partially depolymerised methyl cellulose2003Ingår i: Rapid Communications in Mass Spectrometry, ISSN 0951-4198, E-ISSN 1097-0231, Vol. 17, nr 11, s. 1116-1124Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Methyl cellulose (MC) was partially depolymerised and the oligomers thus obtained were studied by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOFMS). The depolymerisation was either enzymatic or acidic. Fractions of enzymatically depolymerised MC were collected from size-exclusion chromatography and subjected to a sample preparation investigation. Several MALDI matrices and solvents were evaluated. The results showed that the solvent choice had a significant effect on the measured degree of substitution (DS). Aprotic solvents produced higher DS values, which was most likely due to poor solubility of species with low DS. The obtained signal intensity, however, did not correlate with the solubility but seemed to be more dependent on certain matrix/solvent combinations. All the matrices attempted produced mass spectra with sufficient signal intensity for accurate peak area calculation. The choice of matrix did not have any significant effect on the measured DS. Sample spots obtained from organic solvents had a more homogeneous distribution of the analyte and smaller crystals than those obtained from water. This increased both the reproducibility and peak resolution and in addition the analysis time was shorter. DS measurements were performed on two acidically depolymerised MCs with different nominal DS values. It was easy to distinguish between the two MCs, and the measured DS values agreed well with the values supplied by the manufacturers.

  • 16. Richardson, S.
    et al.
    Nilsson, G.
    Cohen, A.
    Momcilovic, Dane
    Brinkmalm, G.
    Gorton, L.
    Enzyme-aided investigation of the substituent distribution in cationic potato amylopectin starch2003Ingår i: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 75, nr 23, s. 6499-6508Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The distribution of substituents along the polymer chain in cationic potato amylopectin starch, modified in solution, granular slurry, or dry state, was investigated. The starch derivatives were successively hydrolyzed by different enzymes, followed by characterization of the hydrolysis products obtained by means of electrospray mass spectrometry (ESI-MS) and matrix-assisted laser desorption/ ionization mass spectrometry (MALDI-MS). ESI-MS and MALDI-MS were proved to be appropriate techniques for identification of the substituted hydrolysis products, for which there are no standard compounds available. No highly substituted oligomers were found in the hydrolysates, which was taken as an indication of a more or less homogeneous distribution of cationic groups in the amylopectin molecules. Furthermore, from the results obtained it was suggested that the enzymes cleave glucosidic linkages only between unsubstituted glucose units and, preferentially, linkages in sequences containing more than two adjacent unsubstituted units. The determination of the amount of unsubstituted glucose produced from every successive hydrolysis step revealed slight differences between the different starch samples with respect to the homogeneity of the substitution pattern. Among the three samples under investigation, starch cationized in solution was found to have the most and dry-cationized starch the least homogeneous distribution of substituents.

  • 17. Schagerlof, H.
    et al.
    Richardson, S.
    Momcilovic, Dane
    Brinkmalm, G.
    Wittgren, B.
    Tjerneld, F.
    Characterization of chemical substitution of hydroxypropyl cellulose using enzymatic degradation2006Ingår i: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 7, nr 1, s. 80-85Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The distribution of substituents along the polymer backbone will have a strong influence on the properties of modified cellulose. Endoglucanases were used to degrade a series of hydroxypropyl cellulose (HPC) derivatives with a high degree of substitution. The HPCs were characterized with cloud-point analysis prior to degradation. The extent of enzymatic degradation was determined with size-exclusion chromatography with online multi-angle light scattering and refractive index detection and also with high-pH anion exchange chromatography with pulsed amperometric detection. To further characterize the formed products, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry was employed for analysis of short-chained oligosaccharides. The different endoglucanases showed varying degradation capability depending on structure of the active site. The highly substituted HPCs had different susceptibility to degradation by the endoglucanases. The results show a difference in substituent distribution between HPCs, which would explain the differing cloud-point behaviors. Increased number of regions with low substitution could be, correlated with lower polymer cloud point. The study shows the usefulness of enzymatic degradation to study the distribution of substituents in soluble biopolymer derivates.

  • 18. Schagerlof, U.
    et al.
    Schagerlof, H.
    Momcilovic, Dane
    Brinkmalm, G.
    Tjerneld, F.
    Endoglucanase sensitivity for substituents in methyl cellulose hydrolysis studied using MALDI-TOFMS for oligosaccharide analysis and structural analysis of enzyme active sites2007Ingår i: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 8, nr 8, s. 2358-2365Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The properties of modified cellulose polymers, such as methylcellulose, are significantly influenced by the distribution of substituents along the polymer backbone. This distribution is difficult to determine due to the lack of suitable analytical methods. One approach is to use cellulose-degrading enzymes to gain information from the capability of the enzymes to cleave the bonds between glucose units. Endoglucanases are cellulase enzymes that can break internal glycosidic linkages and degrade low substituted regions of modified cellulose where the substituents do not interfere with the enzyme active site. In this work methyl cellulose was degraded using five endoglucanases from glycosyl hydrolase families 5 and 7 from three different species. The products were analyzed with reducing end analysis, chromatography (SEC-MALS-RI), and MALDI-TOFMS. The results were correlated with available determined enzyme structures and using structural alignment for unknown enzyme structures. This was performed in order to elucidate the relationship between active site structures and sensitivity for substituents on derivatized cellulose. The evaluation of endoglucanase hydrolysis of methyl cellulose showed that differences in sensitivity could be related to differences in steric hindrance of substituents in the active site, which could explain differences within family 5 and 7 enzymes, as well as the generally higher substituent tolerance for family 5 enzymes. This information is important for use of endoglucanases as tools for characterization of substituent distribution. The results are also valuable since soluble cellulose derivatives are generally used as substrates during enzyme characterization and in endoglucanase activity assays.

  • 19.
    Westberg, Åsa
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Momcilovic, Dane
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Björk, Folke
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsteknik.
    Karlsson, Sigbritt
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Investigation of the emissions from an acrylate and a carpet adhesive in humid and alkaline environments by the micro-scale headspace vial (MHV) method2010Ingår i: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 95, nr 9, s. 1877-1882Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this study, emissions from a carpet adhesive and an acrylate dispersion in simulated humid and alkaline environments were investigated by the micro-scale head space vial (MHV) method. Relative humidity (RH) levels of 75%, 86% and 93% were tested in combination with pH values in the range 10-13. The polymeric materials were exposed at these conditions in sealed 20 mL headspace vials. Chemical analysis of the volatile emission products was performed by headspace solid-phase micro-extraction with subsequent gas chromatography mass spectrometry after three and 36 days. The effect of the RH and pH on the emissions was investigated. It was found that 2-ethyl-1-hexanol was one of the major volatile constituents, and that the emissions of this compound increased dramatically for pH > 12. This can be explained by alkali catalyzed hydrolysis of ester-linked 2-ethylhexyl groups. The other compounds that were detected after exposure of the adhesive were not as strongly dependant on pH and RH as 2-ethyl-1-hexanol. (C) 2010 Elsevier Ltd. All rights reserved.

  • 20.
    Westberg, Åsa
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Momcilovic, Dane
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Björk, Folke
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap.
    Karlsson, Sigbritt
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Quality assessment of building products by the micro-scale headspace vial (MHV) method and HS-SPME for monitoring the emission of hydrolysis products from phthalates2009Ingår i: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 94, nr 6, s. 914-920Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    2-Ethyl hexanol from hydrolysed di-octyl-phthalate (DOP) may cause a secondary emission from building products such as PVC carpets and/or glues causing indoor air pollution. In the present study, a micro-scale headspace vial (MHV) method, earlier developed by us, was refined to study the degradation of DOP and di-isononyl phthalate (DINP) in humid and alkaline environments. By HS-SPME it was possible to extract the degradation products at low temperature, 35 degrees C, which limits the risks of unwanted degradation during sampling. Three different types of HS-SPME fibres were evaluated. The carbowax-divinyl benzene (CW/DVB) fibre had the highest extraction capacity of 2-ethyl-1-hexanol and 5-nonanol. Although significantly shorter extraction times could be used with the 7 mu m and 30 mu m poly-dimethylsiloxane (PDMS) fibres, the CW/DVB fibre was found to be the most suitable for these alcohols. Furthermore, it was found that pH of the alkaline environment strongly influences the formation of degradation products from DOP and DINP.

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