Antibacterial properties of polypropylene textiles modified by poly(2-(N,N-dimethyloamino ethyl) methacrylate)

Polypropylene nonwoven fabrics samples were modified using poly(2-(N,N-dimethyloamino ethyl) methacrylate) (PDAMA) and silver-containing layers. The structure of the material after modification was confirmed using scanning electron mocroscope, energy-dispersive X-ray spectroscopy, Fourier Transfer Infrared Spectroscopy (FTIR), and electro-kinetic measurements. It was found that samples with external PDAMA layers have excellent activity against Staphylococcus aureus under dynamic contact conditions. In contrast, samples finished with deposited silver showed little antimicrobial effect. Antibacterial tests conducted under static conditions showed no antibacterial activity irrespective of the deposited layers.     

N,N,N-trimethyl chitosan nanoparticles as a vitamin carrier system

There is considerable interest in incorporating stabilized vitamins into biopolymeric nanoparticles, especially in the development of carriers and active systems for pharmaceutical and food applications. Amongst biopolymer, chitosan is highly desirable owing to its good biocompatibility, biodegradability and ability to be chemically modified. In this paper, nanoparticles from three kinds of water-soluble derivative chitosan (N,N,N-trimethyl chitosan, TMC) have successfully been synthesized by ionic gelation with tripolyphosphate (TPP) anions. Combinations of concentrations of TMC and TPP have resulted in nanoparticles with varying sizes for which the capability for loading with vitamins was investigated. Zeta potential measurement and particle size analysis demonstrated that the size of the nanoparticles was optimized (196 ± 8 nm) when the lowest TMC and TPP amounts were used, i.e., 0.86 mg mL⁻¹ and 0.114 mg mL⁻¹ respectively. As the TMC and/or the TPP concentrations increase, the resulting size of the nanoparticles increases considerably. Three different vitamins (B9, B12 and C) were tested as additives and the final system characterized in relation to size, morphology, spectroscopic and zeta potential properties. In general, the incorporation of vitamins increased all the TMC–TPP original nanoparticle sizes, reaching a maximum diameter of 534 ± 20 nm when loaded with vitamin C. The presence of vitamins also decreases the zeta potential, with one exception observed when using vitamin C. The preliminary results of this study suggested that all TMC/TPP nanoparticles can be successfully used as a stable medium to incorporate and transport vitamins, with potential applications in foodstuffs.     

Essential role of Ubr11, but not Ubr1, as an N‐end rule ubiquitin ligase in Schizosaccharomyces pombe

The N‐end rule pathway degrades proteins bearing a destabilization‐inducing amino acid at the N‐terminus. In this proteolytic system, Ubr ubiquitin ligases recognize and ubiquitylate substrates intended for degradation. Schizosaccharomyces pombe has two similar Ubr proteins, Ubr1 and Ubr11. Both proteins have unique roles in various cellular processes, although the ubr1? strain shows more severe defects. However, their involvement in the N‐end rule pathway is unclear, and even the N‐end rule pathway‐dependent proteolytic activity has not been demonstrated in Sz. pombe. Here, we show that: (a) Sz. pombe has the N‐end rule pathway in which only Ubr11, but not Ubr1, is responsible; and (b) the C‐terminal fragment of the meiotic cohesin Rec8 (denoted as Rec8c) generated by separase‐mediated cleavage is an endogenous substrate of the N‐end rule pathway. Forced overexpression of stable Rec8c was deleterious in mitosis and caused a loss of the mini‐chromosome. In unperturbed mitosis without overexpression, the rate of mini‐chromosome loss was five‐fold higher in the ubr11? strain. Since Rec8 is normally produced in meiosis, we examined whether meiosis and sporulation were affected in the ubr11? strain. In unperturbed meiosis, chromosome segregation occurred almost normally and viable spores were produced in the ubr11? cells, irrespective of the presence of undegraded endogenous Rec8c peptides. Copyright © 2012 John Wiley & Sons, Ltd.     

Evaluation of the fixed nitrogen-to-protein (N:P) conversion factor (6.25) versus ingredient specific N:P conversion factors in feedstuffs

BACKGROUND: The crude protein (CP) of feedstuffs is important as an indicator of essential and non‐essential amino acids for livestock. The protein (P) level needs to be known accurately, to minimize the feeding of excess nitrogen (N) and to reduce N pollution. Laboratory methods for determining N content report N from amino acids, but also N from ammonia and from non‐amino acid sources. The determined CP based on 6.25 × N level typically overestimates the true protein of feedstuffs. RESULTS: Determined ingredient‐specific N:P conversion factors k_A, k_P and k were not equal to the standard 6.25 factor. The k_A had the highest value in all ingredients, which leads to the estimation of specific crude protein (SCP), which is closer to true protein (the summation of the total amino acid residues from amino acid analyses). The SCP(k_A) was lower than CP and true protein in all ingredients, demonstrating that CP might overestimate the actual protein in feedstuffs. CONCLUSION: Based on data from 677 feedstuff samples from 2009, it is concluded that the mean k_A should be 5.68 for corn, 5.64 for soybean meal, 5.74 for corn DDGS, 5.45 for poultry by‐product meal and 5.37 for meat and bone meal. Copyright © 2011 Society of Chemical Industry     

Uptake of foliar-applied urea by winter wheat (Triticum aestivum): The influence of application time and the use of a new 15N technique

A new ¹⁵N technique (termed the negative discard method) for measuring recovery of foliar-applied N by crops in the field is described. ¹⁵N-labelled fertiliser solution is sprayed on to a small area of crop, using a hand sprayer, while the surrounding area is sprayed with unlabelled N at the same rate. An area considerably larger than that given ¹⁵N is harvested with a small-plot combine-harvester, and crop recovery of foliar-applied N is calculated from the ¹⁵N enrichment of the resulting sample containing a mixture of labelled and unlabelled material. The technique was used to measure recovery of N from ¹⁵N-labelled urea solution sprayed on to winter wheat (Triticum aestivum L cv Avalon) at six different times from growth stage 39 (3 weeks before anthesis) to growth stage 73 (2 weeks after anthesis). Each treatment of 40 kg N ha^?1 was divided into two equal portions, the second being applied 1–2 days after the first, to minimise the risk of leaf damage. The crop had earlier received 210 kg N ha^?1, as ‘Nitro-Chalk’, in spring (50 kg ha^?1 at growth stage 22 and 160 kg ha^?1 at growth stage 31) which was more than sufficient to achieve maximum grain yield. At harvest, 70% of the foliar-applied N given at anthesis (growth stage 65) was recovered in the above-ground crop, including 64 % in grain. The proportion of labelled N recovered in the grain (92% of that in the above-ground crop) was slightly greater than with soil-applied N given earlier in the growing season. Recovery of foliar-applied N was slightly less for the earliest (growth stage 39) and latest (growth stage 73) times of spraying: 64% and 58% in above-ground crop, and 56% and 54% in grain, respectively. All of the foliar applications of 40 kg N ha^?1 increased %N in grain to the same extent as an additional 40 kg N ha^?1 applied to soil in spring.     

N,N‐Bis(2‐hydroxyethyl)formamide as a New Plasticizer for Thermoplastic Starch

N,N‐Bis(2‐hydroxyethyl)formamide (BHF) was synthesized efficiently and used as a new plasticizer for corn starch to prepare thermoplastic starch (TPS). The hydrogen bond interaction between BHF and starch was proven by Fourier‐transform infrared (FT‐IR) spectroscopy. As detected by scanning electron microscopy (SEM), starch granules were completely disrupted and a continuous phase was obtained. The crystallinity of corn starch and BHF‐plasticized TPS (BTPS) was characterized by X‐ray diffraction (XRD). The thermal behavior of glycerol‐plasticized TPS (GTPS) and BTPS was investigated by differential scanning calorimetry (DSC). The water resistance of BTPS was better than that of GTPS. Generally, at low relative humidity (RH), the tensile strength of BTPS was higher than that of GTPS. At high RH, the elongation at break of BTPS was higher than that of GTPS.     

Partitioning into maize grain N fractions of N absorbed through the roots before and after pollination

The abundance of N in various fractions in maize (Zea mays L.) grain was compared in two genotypes, a normal hybrid (Pioneer 3369A) and its opaque-2 (o-2) counterpart (L3369). Plants were grown in the greenhouse in sand cultures irrigated daily with nutrient solutions containing 3.75mM N as NO₃ ion. At anthesis the plant cultures were divided into sets, one set continuing to be irrigated with the same solution, but with ¹⁵N added, and the other set irrigated with a solution of the same composition except that the N was omitted. The plants were sampled at 12, 24 and 36 days after pollination. Post-anthesis N nutrition affected the composition of the vegetative growth but had no effect during the sampling period on yields or amounts of N in the grain. At 12 days post-pollination there were no differences between the two genotypes in N partitioning, with about 50% of the N present as nonprotein N (NPN). At 24 and 36 days over 75% more N was present as zein in the normal genotype as in the 0-2, while the latter contained a much higher proportion of N as NPN. The albumin-globulin and glutelin fractions were slightly greater in the o-2. The N absorbed after pollination was partitioned among the grain protein fractions similarly to N absorbed prior to pollination. The nature of the NPN fraction needs to be considered in evaluating effects on crop quality of an elevated N supply.     

The influence of yeast immobilization on selected parameters of young meads

Mead is a traditional product derived from the fermentation of diluted honey. The main purpose of the study was to determine the influence of Saccharomyces cerevisiae immobilization in calcium alginate, κ‐carrageenan and lightly crosslinked poly(acrylic acid) on fundamental enological parameters and concentrations of formic and acetic acids (SPME‐GC) in fermented mead worts. Ionic hydrogels, especially poly(acrylic acid) and κ‐carrageenan, increase the ethanol concentration (up to 18% v /v) in young meads and reduce titratable (35%) and volatile acidity (67%), primarily by decreasing acetic acid synthesis with the use of immobilized cells of yeast. The surface immobilization on poly(acrylic acid) resulted in a reduction of the time of fermentation by about 25 days. The immobilization of yeast inside calcium alginate and κ‐carrageenan gels extended the time of preliminary fermentation and reduced the degree of fermentation in samples with calcium alginate. Copyright © 2017 The Institute of Brewing & Distilling     

Quality of white cabbage yield and potential risk of ground water nitrogen pollution,as affected by nitrogen fertilisation and irrigation practices

BACKGROUND: The effect of different fertilisation (broadcast solid NPK application and fertigation with water‐soluble fertiliser) and irrigation practices (sprinkler and drip irrigation) on yield, the nitrate content in cabbage (Brassica oleracea var. capitata L.) and the cabbage N uptake was detected, in order to assess the potential risk for N losses, by cultivation on sandy–loam soil. The N rate applied on the plots was 200 kg N ha^?1. RESULTS: The highest yield (93 t ha^?1) and nitrate content (1256 mg kg^?1 DW) were found with treatments using broadcast fertilisation and sprinkler irrigation. On those plots the negative N balance (?30 kg N ha^?1) was recorded, which comes mainly from the highest crop N uptake (234 kg N ha^?1) indicating the lowest potential for N losses. CONCLUSION: In terms of yield quality and the potential risk for N losses, broadcast fertilisation combined with sprinkler irrigation proved to be the most effective combination among the tested practices under the given experimental conditions. The importance of adequate irrigation is also evident, namely in plots on which 50% drip irrigation was applied, the lowest yield was detected and according to the positive N balance, a higher potential for N losses is expected. Copyright © 2011 Society of Chemical Industry     

Effects of different carbon sources and C/N values on nonvolatile taste components of Pleurotus eryngii

Pleurotus eryngii, the second largest industrial cultivation mushroom in China, is usually cultivated on substrates mainly consisting of sawdust and corncob. In this study, experiments were performed to determine the effects of different carbon sources and C/N values on nonvolatile taste components of P. eryngii. The effects of different carbon sources on nonvolatile taste components levels revealed that sawdust was beneficial to high levels of crude protein, amino acids, 5′‐nucleotides and equivalent umami concentration, while corncob was beneficial to high contents of carbohydrate, polysaccharides and trehalose. At the similar C/N values, relatively higher sawdust content was beneficial to umami amino acid production, while relatively higher corncob content was beneficial to high contents of carbohydrate, polysaccharides and mannitol. Higher C/N value was beneficial to high levels of crude protein, amino acids, 5′‐nucleotides and equivalent umami concentration, while lower C/N value was beneficial to high contents of carbohydrate, polysaccharides and trehalose. These results provided information for P. eryngii fruit body industrial cultivation to obtain specific nonvolatile taste components with high levels.     

Evaluation Antibacterial Activity of Quaternary‐Based Chitin/Chitosan Derivatives In Vitro

Abstract: Total of 3 water‐soluble quaternary‐based chitin/chitosan derivatives, which have an identical molecular weight and anion, were synthesized and characterized. Their antibacterial activities against Salmonella cholerae‐suis and Bacillus subtilis were evaluated in vitro. The polysaccharides exhibited the antibacterial efficiency. Their minimum inhibitory concentration (MIC) values vary from 0.02 to 20.48 mg/mL, and their minimum bactericidal concentration (MBC) values vary from 0.08 to 40.96 mg/mL against S. cholerae‐suis and B. subtilis, respectively. Futhermore, the extent of Bacillus subtilis cells damage was examined via transmission electron microscopy (TEM) to show how N,N,N‐trimethylchitosan (TMC) gradually destroyed and killed B. subtilis cells when they were treated with TMC. One of those quaternary polymers, O‐([2‐hydroxy‐3‐trimethylammonium])propyl chitin (OHT‐chitin), which can be directly and easily synthesized from chitin in bulk quantities, also was demonstrated its antibacterial activity. These water soluble quaternary‐based chitin/chitosan derivatives that have antibacterial effect should be potentially used as antimicrobial agents in many fields. Practical Application: The main practical application behind the investigation and evaluation antibacterial activity of 3 water‐soluble quaternary‐based chitin/chitosan derivatives could be potentially used as antimicrobial agents in many fields. These polysaccharides represent a renewable source of natural biodegradable polymers and meet with the emergence of more and more food safe problems.     

Relative proportion of inorganic and total nitrogen in broiler litter as determined by various methods

We report relative proportion of inorganic N in broiler litter and compare the regular Kjeldahl method with three of its modifications (the salicylic acid–thiosulfate modification, the Devarda's alloy modification, and the potassium permanganate–reduced iron modification), and with a Leco‐combustion (CHN‐600) method for the degree to which they include NO₃^?‐N and NO₂^?‐N in broiler litter analysis. Inorganic N in the litter (<500 µm) was determined after extraction with 2 mol L^?1 KCl. NH₄⁺‐N and (NO₃^? + NO₂^?)‐N in the filtrate were analysed by steam distillation while NO₂^?‐N was determined by a modified Griess–Ilosvay colorimetric method. For the determination of total N, 25 mg broiler litter (<1000 µm) was digested according to four semi‐micro‐Kjeldahl methods in a 100‐mL Pyrex Kjeldahl flask using an electrically heated six‐flask micro‐Kjeldahl digestion rack. Ammonium‐N in the digest was determined by steam distillation. The results showed that inorganic N represents a small portion of total N in the samples. Ammonium is the most dominant inorganic N (1.61–5.39 g kg^?1) in the samples; it represents between 42 and 94% of the inorganic N. The (NO₃^? + NO₂^?)‐N contents varied between 0.19 and 5.56 g kg^?1 while NO₂^?‐N contents in the samples were negligible (<0.6 g kg^?1). The regular Kjeldahl method and its modifications recovered all the NH₄⁺‐N added but recovery of added NO₂^?‐N and NO₃^?‐N varied considerably with the methods. The Devarda's alloy and the potassium permanganate methods showed the highest N measurements while the Leco‐combustion showed the lowest N measurements. Copyright © 2006 Society of Chemical Industry     

The fertiliser nitrogen requirement of cereals grown on sandy soils

The responses to fertiliser‐N of winter wheat and winter barley grown on sandy soils were measured in 72 experiments in England from 1990 to 1994. Yield without fertiliser‐N (Y₀) was c 1.1 t ha⁻¹ greater following root crops than following cereals. Following potato crops given organic manures, Y₀ was c 1.2 t ha⁻¹ greater than following unmanured potato crops, but Y₀ was no greater following sugarbeet to which organic manures had been applied. Only after the two driest winters was there sufficient variation in soil N supply in spring (SNS_s) for this to show a relationship with Y₀. However, Y₀ increased with increasing N mineralisation during the growing season (AM) in the three years it was measured. There was no consistent effect of sowing date on Y₀. Following potatoes, yield at optimum fertiliser‐N (Y_opt) decreased as sowing date was delayed, but this was not so after cereals, sugarbeet or overall. There was no increase in Y_opt with SNS_S or AM, but Y_opt decreased with increasing moisture stress (S) in June. The mean yield response to N_opt (Δ_Y) was c 0.4 and 0.8 t ha⁻¹ smaller following potatoes and sugarbeet respectively than following cereals, but not consistently so as there were large interactions between site, year and previous crop. Following root crops, Δ_Y was c 0.6 and 1.4 t ha⁻¹ less after sugarbeet and potatoes respectively that had been given organic manures. Without the addition of organic manures, Δ_Y following potatoes was similar to that following cereals. Regression on SNS_S and AM accounted for 28 and 15% respectively of the variance in Δ_Y. The optimum economic fertiliser‐N application (N_opt) was similar, at c 140 kg ha⁻¹, following cereals and potatoes. Following sugarbeet, cereal N_opt was only c 110 kg ha⁻¹. The differences according to previous crop reported here are consistent with mineralisation of crop residues on sandy soils being more rapid than on other soils; the potato residues were rapidly mineralised in autumn and lost by leaching over winter. Residues from later‐harvested sugarbeet were mineralised during the growing season of the subsequent cereal crop. Fertiliser‐N requirements were, at c 110–140 kg ha⁻¹, smaller than has been found on other soil types, and less than current recommendations for wheat. Requirements were significantly reduced in years of drought stress. No differences were found in N_opt between wheat and barley. These data do not justify the current advice to invariably reduce fertiliser‐N to cereals following potatoes by 20–25 kg ha⁻¹ on these sandy soils. On average a reduction of c 20 kg ha⁻¹ could be made following sugarbeet, with a further reduction of c 40 kg ha⁻¹ N if manures had been applied to the previous sugarbeet crop. A reduction of 40 kg ha⁻¹ N could also be made where cereals followed a potato crop to which manures had been applied. Further refinements on the basis of measurements of soil mineral N could not be justified. Seasonal variation in N response due to drought stress makes recommendations difficult on these soils. Adopting the fertiliser‐N recommendations proposed here would produce N surpluses to the soil of c 37, 10 and 27 kg ha⁻¹ respectively following cereals, sugarbeet and potatoes when cereal grain is removed but straw incorporated. On farms where straw is removed, N surplus would be largely eliminated. Our recommendation that no reduction in fertiliser‐N application to cereal crops grown on sandy soils should be made following potatoes will not increase fertiliser‐N use and is not expected to increase nitrate leaching. Some reduction in nitrate leaching may be achieved if recommendations following cereal crops and sugarbeet are made in accordance with the results reported here. © 2000 Society of Chemical Industry     

Nitrogenase Activity and Nitrogen-Fixing Bacteria Associated with Rhizosphere of Rice Cultivars with Varying N Absorption Efficiency

In a field investigation, nitrogenase activity and nitrogen-fixing bacteria associated with rhizosphere of rice cultivars with varying N absorption efficiencies were examined at three N-fertiliser regimes. A significant difference among the cultivars with regard to the nitrogenase activity of rhizosphere bacteria was observed. Under no or low (30 kg N ha^-1) fertiliser application, the cultivar with high boot leaf-N and high apparent N recovery had a higher nitrogenase activity. At 60 kg N ha^-1 fertiliser application, though the nitrogenase activity was stimulated, the differences with regard to nitrogenase activity among the cultivars were not significant. Microbiological analysis indicated that the cultivar with high N absorption efficiency harboured higher populations of nitrogen-fixing Azospirillum sp, Azotobacter sp and anaerobic bacteria. Under 60 kg N ha^-1 fertiliser application, the rhizosphere of both cultivars, which differed in their N use pattern, harboured almost identical population densities of nitrogen-fixing bacteria. Interestingly, the anaerobic nitrogen-fixing bacteria were greatly stimulated following the application of fertiliser. Notwithstanding the effect of N fertiliser management on N₂ fixation, N absorption efficiency of rice crop and the rhizosphere associated nitrogenase activity and nitrogen-fixing bacteria were found to be interrelated. Further investigations are required to evaluate the exact relationships including higher number of cultivars. © 1997 SCI.     

Effect of plant polyphenols and ascorbic acid on lipid oxidation,residual nitrite and N‐nitrosamines formation in dry‐cured sausage

The effects of green tea,grape seed polyphenols and ascorbic acid on pH, water activity (a_w), microbiological counts, TBARS, residual nitrite and N‐nitrosamines were determined in dry‐cured sausages during the ripening period. Results showed that TBARS increased gradually during ripening (P < 0.05), but were significantly reduced with plant polyphenols and ascorbic acid (P < 0.05). Green tea polyphenol (GTP) was most effective (P < 0.05) in reducing TBARS. Plant polyphenols and ascorbic acid significantly decreased residual nitrite, ascorbic acid being most effective (P < 0.05). The amount of N‐nitrosamines increased during ripening, but was significantly reduced with plant polyphenols and ascorbic acid (P < 0.05). Plant polyphenols had no significant effects on moisture content, a_w, pH or microbiological counts in dry‐cured sausage during ripening (P > 0.05). It was concluded that plant polyphenols and ascorbic acid were effective in maintaining the quality and safety of dry‐cured sausages.     

Interactions between the kernel N sink, grain yield and protein nutritional quality of maize

The isogenic opaque-2 (o2) and its normal counterpart of maize (Zea mays L.) hybrid ‘B14 × B37’ were used as a model system and grown under different levels of nitrogen fertility to test the importance of the kernel N sink (zein accumulation) relative to kernel osmotic potential, dry matter accumulation, grain yield and protein nutritional quality. Self-pollination and reciprocal crosses were made with seven o2 hybrids and their normal counterparts in order to determine the effect of the kernel N sink and/or vegetative characteristics on kernel dry weight accumulation. The results indicate that with a small supply of nitrogen, both normal and o2 kernels produced only small amounts of zein, and kernel weights and grain yields were comparable. As the level of nitrogen increased, zein accumulated preferentially in normal, but not in o2, and differences in kernel weight and grain yield between these two genotypes became greater. The reduction of dry matter accumulation in o2 kernels relative to normal kernels when grown under high N levels may result from the accumulation of free amino acids and their catabolic products in the kernel as a consequence of a small N sink. These osmotica contributed to a more negative osmotic potential which may favour water movement, but reduce solute movement into the kernel. Increased zein accumulation in normal kernels enhanced kernel weight and grain yield but reduced protein nutritional quality. The concentration of lysine and tryptophan as a percentage of protein decreased as the level of N fertiliser and kernel protein in the normal kernel increased. On the other hand, the o2 mutant failed to deposit additional N as zein; therefore, the concentration of these two essential amino acids remained constant regardless of N levels. However, when lysine and tryptophan were expressed on an area (kg ha^?1) basis, the amino acid yields of these two genotypes were comparable.     

Production of Higher Alcohols and Short Chain Fatty Acids by Different Yeasts Used in Rum Fermentations

The production of higher alcohols and short chain fatty acids by yeasts used in rum fermentations was greater by the Saccharomyces strains than by those belonging to the Schizosaccharomyces genus. There were also qualitative differences between these two genera. Among the organic acids of the raw material, citric acid and cisaconitic acid constitute a special feature of the composition of the resulting rums. Their presence entails the abundant production of biomass. Citric acid alone induced acrylic acid formation by strains of two species among the three studied.     

Potential isotopic and chemical markers for characterising organic fruits

Several isotopic (¹³C/¹²C, ¹⁵N/¹⁴N, ¹⁸O/¹⁶O, ²H/¹H, ³⁴S/³²S) and chemical–physical parameters (pH, fruit weight, juice yield, titratable acidity, total soluble solids, skin resistance, flesh firmness, colorimetric characteristics, weight loss after harvesting, antioxidant activity, earliness index, total nitrogen, ascorbic acid, synephrine, anthocyanins and polyphenols, citric acid, malic acid, sucrose, glucose and fructose content) were investigated as potential markers of organically cultivated oranges, clementines, strawberries and peaches produced in Italy between 2006 and 2008, in experimental fields and in certified farms. The ratio ¹⁵N/¹⁴N, ascorbic acid and total soluble solids were shown to be the most significant variables for distinguishing between organically and conventionally cultivated fruits. It was not possible to define general threshold limits typical of organic fruits because these parameters are influenced also by fruit specie, cultivar, year and site of production. Combining isotopic and chemical markers a good discrimination between organic and conventional fruits of different species was achieved.     

交联型醋丙乳液用于汽车滤纸的增强

使用共聚和交联共用的方法对汽车滤纸用醋丙乳液增强剂进行改性,研究了体系中甲基丙烯酸甲酯(MMA)、丙烯酸(AA)、N-羟甲基丙烯酰胺(NMA)和三聚氰胺甲醛树脂(MF)用量对浸渍后滤纸强度性能的影响。结果表明,在MMA用量20%(质量分数,下同)、AA用量3%、NMA用量5%、MF用量4%时,改性醋丙乳液可赋予滤纸优良的强度性能,同时保持滤纸优良的孔隙结构和透气性。     

Degradation of N‐(1‐Deoxy‐d‐xylulos‐1‐yl)glycine and N‐(1‐Deoxy‐d‐xylulos‐1‐yl)proline using thermal treatment

The formation and degradation of N‐(1‐Deoxy‐d ‐xylulos‐1‐yl)glycine and N‐(1‐Deoxy‐d ‐xylulos‐1‐yl)proline, derived from the secondary amine Maillard reaction in xylose‐amino acid model solutions, were detailed in this study. The identification and quantitative analysis of N‐(1‐Deoxy‐d‐ xylulos‐1‐yl)glycine and N‐(1‐Deoxy‐d‐ xylulos‐1‐yl)proline were carried out using high‐performance anion‐exchange chromatography and high‐performance liquid chromatography. The formation of intermediate and advanced products derived from N‐(1‐Deoxy‐d‐ xylulos‐1‐yl)glycine and N‐(1‐Deoxy‐d‐ xylulos‐1‐yl)proline was also tested using an UV‐Vis spectrophotometer to gain a better comparing of the degradation process of the two important Maillard reaction products using thermal treatment. Results showed that the degradation of N‐(1‐Deoxy‐d‐ xylulos‐1‐yl)glycine was more significant than N‐(1‐Deoxy‐d‐ xylulos‐1‐yl)proline. Moreover, xylose was tested in the degradation products of both N‐(1‐Deoxy‐d‐ xylulos‐1‐yl)glycine and N‐(1‐Deoxy‐d‐ xylulos‐1‐yl)proline, which indicated that the degradation of N‐substituted 1‐amino‐1‐deoxyketoses was a reversible reaction to form reducing sugar.