Cross-linking behavior and foaming properties of bovine α-lactalbumin after glycation with various saccharides

α-Lactalbumin was glycated via the Maillard reaction in the dry state using various mono- and oligosaccharides. The reaction resulted not only in coupling of the saccharides to α-lactalbumin but also in cross-linked proteins. The glycation rate and the extent of cross-link formation were highly dependent on the saccharide used. Glycation by arabinose and xylose led to a very fast protein cross-link formation, whereas glucose showed a relatively low protein cross-linking ability. The stability of foams, created using the various glycated protein samples, depended on the type of saccharide used, the extent of glycation, and possibly the amount of cross-linked protein. Compared to nonmodified α-lactalbumin, glycation with rhamnose and fucose improved foam stability, whereas application of glucose, galacturonic acid, and their oligosaccharides did not exert a clear effect. Mass spectrometric analysis revealed that dehydration of the Amadori products is an indicator of the formation of protein cross-links.     

Identification of the peroxidase-generated intermolecular dityrosine cross-link in bovine α-lactalbumin

The peroxidase-mediated oxidation of calcium-depleted bovine α-lactalbumin generates a mixture of covalently bound protein oligomers with interesting foaming properties. Here, we isolated the initially formed covalent α-lactalbumin dimer and studied its mode of cross-linking. Liquid chromatography-Fourier transform mass spectrometry (LC-FTMS) of proteolytic digests revealed the unambiguous identification of a peroxidase-catalyzed covalent link between Tyr18 and Tyr50. This shows that, although the radical reaction is often regarded as a random reaction, the initial product formation is specific. Protein structural modeling indicates that the conjugation reaction between these tyrosines is sterically favored and involves initial noncovalent protein complex formation through charge compensation, facilitating intermolecular cross-linking. The identification of the Tyr18-Tyr50 cross-link supports the view that the peroxidase-mediated oxidation of apo α-lactalbumin is a sequential process, involving the formation of linear trimers and higher order oligomers.     

Seeds capture the diversity of genetic resource collections of <Emphasis Type="Italic">Malus sieversii</Emphasis> maintained in an orchard

Many species in genebank collections are maintained vegetatively either as in vitro cultures or as plants in the field or greenhouse. In these cases, individual genotypes (cultivars) are the focus of conservation. In crop wild relatives, where the value of an accession is in the heterogeneity of segregating genotypes, seeds may be the most representative form of conservation. We used two sets of field-planted Malus sieversii apple trees that originated from seeds collected from two wild populations in Kazakhstan as a model system to determine if seeds from hand-pollinated crosses could be used to represent the allelic diversity of the parent trees in a genebank orchard. A crossing design was developed that used each of the selected trees from the two Kazakhstan collection sites as mothers and also as fathers in the form of bulked pollen pools. The sets of offspring from these crosses were genotyped using microsatellite markers. Paternity analyses revealed the percentage of offspring that was derived from each of the parent trees. We also determined the contribution of each parent to the fertilization events from the pollen pools. Although there were some unintended pollination events (fertilization by trees in unexpected pollen pools) and unequal contribution of pollen parents within pollen pools, we demonstrated that the seedlings effectively captured the allelic frequency and diversity of the parents. A seed collection strategy is the most efficient way to conserve the diversity of crop wild relatives even in collections typically conserved as individual clones.     

Modification of glutamine and lysine residues in holo and apo alpha-lactalbumin with microbial transglutaminase

The molecular structures determine the physical properties of milk proteins and are important for the texture of many dairy-based foods. Bovine alpha-lactalbumin (alpha-LA) is a globular 123 amino acid Ca(2+) binding milk protein. Modification with microbial Ca(2+) independent transglutaminase (MTGase) was used to modify lysines and glutamines in holo and apo alpha-LA. At 30 degrees C no lysines or glutamines are modified in holo alpha-LA, whereas in apo alpha-LA lysines 13, 16, 108, and 114, and glutamines 39 and 43, are modified. At 50 degrees C lysines 13, 16, 108, and 114, but no glutamines, are modified in holo alpha-LA, whereas in apo alpha-LA lysines 5, 13, 16, 108, and 114, and glutamines 39, 43, 54, 65, and 117, are modified. The methods presented here offer the possibility to manipulate the availabilities of residues in alpha-LA to the MTGase reaction and enable the preparation of alpha-LA species with different degrees of modification and hence with different physical properties.     

非均匀土壤区域SVAT模型中土壤水动力学参数的整合研究

荷兰Cabauw地区一个 10km10km区域内的四种主要土壤的水动力学参数用一种实验室直接测定法 (Wind氏蒸发法 )和两种间接方法 (分段土壤推导函数、连续土壤推导函数)确定 ,而该区域水动力学特性参数的整合则采用两组方案 (聚合土壤参数法和有效土壤参数法 )进行。一个SVAT模型的模拟输出结果感热通量、潜热通量与实测数据的比较分析表明 :(1)对于用分段土壤推导函数确定的土壤水动力学参数的区域整合 ,以逆模拟法(有效土壤参数法 )较为可行 ,其模拟感热、潜热的精确性接近参比方案 (模拟 平均法) ;(2 )对于实验室直接测定的参数 ,则以几何平均vanGenuchten Mualem经验公式参数的方案 (聚合土壤参数法 )为佳 ;(3)对于连续土壤推导函数推导的水动力学参数 ,几何平均土壤组分方案 (聚合土壤参数法 )和逆模拟法方案 (有效土壤参数法 )二者均可得到优于参比方案 (模拟 平均法)的模拟结果 ,其中以前者最佳 ;(4 )所有区域化参数整合方案中 ,以水平几何平均区域内实验室直接测定的参数的方案最优 ;同时 ,连续土壤推导函数法的土壤组分几何平均方案的模型输出精确性接近该最优方案     

Community patterns of soil bacteria and nematodes in relation to geographic distance

Ecosystems consist of aboveground and belowground subsystems and the structure of their communities is known to change with distance. However, most of this knowledge originates from visible, aboveground components, whereas relatively little is known about how soil community structure varies with distance and if this variability depends on the group of organisms considered. In the present study, we analyzed 30 grasslands from three neighboring chalk hill ridges in southern UK to determine the effect of geographic distance (1–198 km) on the similarity of bacterial communities and of nematode communities in the soil. We found that for both groups, community similarity decayed with distance and that this spatial pattern was not related to changes either in plant community composition or soil chemistry. Site history may have contributed to the observed pattern in the case of nematodes, since the distance effect depended on the presence of different nematode taxa at one of the hill ridges. On the other hand, site-related differences in bacterial community composition alone could not explain the spatial turnover, suggesting that other factors, such as biotic gradients and local dispersal processes that we did not include in our analysis, may be involved in the observed pattern. We conclude that, independently of the variety of causal factors that may be involved, the decay in similarity with geographic distance is a characteristic feature of both communities of soil bacteria and nematodes.     

Application of bio-desalinization for reclamation of salt-affected soil under composted cow manure and deficit irrigation with saline water

Paddy and Water Environment - Application of common leaching and flushing methods is often impractical due to freshwater scarcity, groundwater pollution and a lack of suitable drainage systems. To...     

The prececal and total intestinal nutrient digestibility and amino acid absorption of food yeasts in swine

In a difference experiment the apparent precaecal (pc) and total intestinal (tot) nutrient digestibility and amino acid (AA) absorption of 5 yeasts (n-alkane yeasts Fermosin and Paprin, molasses/molasses distillers residue yeast, two sulfite waste liquor yeasts) were studied. The two n-alkane yeasts were very highly digested pc, the difference to tot digestibility is only small in most cases. In contrast to this, the pc and tot digestibility values of molasses/molasses distillers residue yeast differed considerably more. The probable reason for this is too hot drying due to which pc digestibility, particularly of the crude protein, and pc AA absorption are considerably reduced. In the two sulfite waste liquor yeasts, sulfite waste liquor residues containing lignin impair especially the crude carbohydrate digestibility and the energetic feed value; the better processing conditions of origin A, however, reduced considerably the negative effects. The results confirm that each yeast origin has its specific particularities, which have to be taken into consideration when they are used in feeding.     

Multiplication of Erwinia amylovora in fruit-trees. 1. A simulation study on limitations imposed by temperature and water,weather and soil

Temperature and water may limit multiplication of the fire blight causing bacteriumErwinia amylovora in shoots of fruit-trees. To gain insight into these limitation under field conditions, two simulation models were designed: a short-term model for immediate effects of weather and soil water potential, and a long-term model for effects of rain and soil profiles on the limitations imposed by temperature and water on bacterial multiplication.In the Netherlands, in the month June, if the soil is moist and the weather average, water hardly limitsE. amylovora multiplication in shoots but, according to the short-term model, temperature reduces then the multiplication by about 60^. When the soil is dry and the potential transpiration rate of the trees high, water may limitE. amylovora multiplication in shoots considerably. According to the long-term model, rain has a delayed effect on multiplication. The effect of rain was simulated for three soil profiles representing three typical fruit growing areas in the Netherlands.     

Characteristics and pathogenicity of six Phytophthora isolates from pot plants

From several greenhouse plants showing foot and root rot symptomsPhytophthora isolates were gathered. Isolates fromPeperomia, Saintpaulia andSinningia were identified asP. nicotianae van Breda de Haan var.nicotianae and an isolate fromBegonia asP. cryptogea Pethybr. & Laff. Cardinal temperatures for the various isolates were determined. The specific and non-specific pathogenicity of the isolates was studied by inoculating the different crops with the different isolates, including aP. cryptogea isolate fromGerbera and aP. nicotianae var.nicotianae isolate from carnation. TheP. nicotianae var.nicotianae isolates appeared to be morphologically identical. Some of the isolates were similar in host range, but others exhibited differences in host specificity at 20°C as well as 25, 30 or 35°C. The same applies for the twoP. cryptogea isolates.