Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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A systematic review of practices to promote vegetable acceptance in the first three years of life
Barends, Coraline ; Weenen, Hugo ; Warren, Janet ; Hetherington, Marion M. ; Graaf, Cees de; Vries, Jeanne H.M. de - \ 2019
Appetite 137 (2019). - ISSN 0195-6663 - p. 174 - 197.
Infants - Introducing vegetables - Systematic review - Toddlers - Vegetable intake

Background: Although most children do not meet vegetable intake recommendations no clear universal guidelines exist on the best method of introducing and promoting vegetables in infants. Objective: To identify strategies to promote vegetable acceptance in children from the start of complementary feeding until 3 years of age. Design: A comprehensive search strategy was performed using the databases Scopus and Pubmed. Articles published before March 2018 measuring vegetable intake and/or liking were included. Results: 46 papers, 25 experimental (intervention) studies, and 21 observational studies were included. Intervention studies revealed that repeated exposure increased acceptance of the target vegetable, whereas exposure to variety was found to be particularly effective in increasing acceptance of a new vegetable. Starting complementary feeding with vegetables increased vegetable acceptance, whereas starting with fruits did not. Visual exposure to an unfamiliar vegetable increased the acceptance of that vegetable even without consuming it, while visual exposure to a familiar vegetable did not. A stepwise introduction of vegetables resulted in better initial acceptance of vegetables than introducing vegetables directly. Observational studies showed that vegetable consumption was associated with frequency of exposure, exposure to variety, and modelling. A majority of studies found a positive association between breastfeeding and vegetable acceptance, but only two out of seven studies found an association between age of vegetable introduction and their acceptance. Conclusions: Based on the papers reviewed, we conclude that introducing vegetables at the beginning of complementary feeding, giving a different type of vegetable every day and ensuring repeated exposure to the same vegetable following an interval of a few days are the most promising strategies to promote vegetable intake in children starting complementary feeding until they are 3 years of age.

Infants’ liking for green beans, based on observed behaviour and facial expressions, increased after repeated exposure to vegetables at the start of weaning
Barends, C. ; Gatzemeier, Jennifer ; Graaf, C. de; Vries, J.H.M. de - \ 2016
Appetite 107 (2016). - ISSN 0195-6663 - p. 677 - 678.
Most children do not consume the recommended amount of vegetables. Liking is an important predictor of intake, therefore the aim of this study was to investigate the effect of repeated vegetable exposure on infants’ liking for green beans, assessed through the observation of acceptance and facial expressions. Four to seven month old infants (N = 101) were randomly assigned to either a vegetable or a fruit group, receiving vegetable or fruit purees for the first 18 days of weaning, respectively. On day 19, the fruit group received their first vegetable puree and vice-versa. For the present study, recordings of 60 mother-infant dyads were analysed. Behavioural responses and acceptance of the approaching spoon as well as negative facial expressions in response to the consumption of green bean puree were recorded and analysed in both groups. Within the vegetable group, infants showed a significant decrease in negative facial expressions and a significant increase in acceptance of green bean puree between baseline and 18 days of exposure. Further, infants in the vegetable group expressed significantly fewer negative facial expressions and a higher acceptance of vegetable puree after the intervention period compared to infants in the fruit group. A significant negative correlation between intake and facial expressions was found. Results support previous findings that liking for vegetables increases through repeated exposure to vegetables, but liking of vegetables does not increase through repeated exposure to fruits.
Application and validation of the Feeding Infants : Behaviour and Facial Expression Coding System (FIBFECS) to assess liking and wanting in infants at the time of complementary feeding
Nekitsing, C. ; Madrelle, J. ; Barends, C. ; Graaf, C. de; Parrott, H. ; Morgan, S. ; Weenen, H. ; Hetherington, M.M. - \ 2016
Food Quality and Preference 48 (2016)Part A. - ISSN 0950-3293 - p. 228 - 237.
Complementary feeding - Facial expressions - Food refusal - Infant feeding - Like/dislike - Liking - Scale - Wanting - Weaning

Introduction: The aim of this study was to validate a novel tool developed to measure liking and wanting in infants during the weaning period. The Feeding Infants: Behaviour and Facial Expression Coding System (FIBFECS; Hetherington et al., in press) is an evidence based video coding tool, consisting of 13 items. There are 6 measures of avoidance/approach behaviours (turns head away, arches back, pushes spoon away, crying/fussy, leaning forward and rate of acceptance) to assess wanting and 7 facial expressions (brow lowered, inner brow raised, squinting, nose wrinkling, lip corners down, upper lip raised and gaping) to assess liking. Lower scores on the total scale indicated greater wanting and/or liking. The tool was applied to a recent randomized control trial (Hetherington et al., 2015). Method: 36 mother-infant dyads took part in the study and were randomised to the intervention or the control group. Infants were filmed on two occasions whilst eating a generally liked vegetable (carrots) and less preferred vegetable (green bean). 72 video extracts were coded by 4 trained researchers with adequate certification scores, each video was coded by at least two coders. Items and scales were tested for discrimination ((1) intervention vs control; (2) liked vs disliked vegetable) and construct validity (correlation with intake and liking assessed by mother and researcher). Results: Very good discrimination (p <0.001) was obtained for carrots vs green bean for the total score and total negative facial expressions and rejection behaviours (p=0.003). Discrimination for the intervention vs control groups was only obtained for the total rejections and the rate of acceptance (p <05). The FIBFECS subscales had good construct validity as these were significantly correlated with intake and liking ratings (p <0.01). Items such as crying/fussy and leaning forward were removed from the scale as well as inner brow raised, squinting and lip corners down, as these do not correlate with other variables. Their removal did not affect the integrity of the scale. The rate of acceptance parameter was found to have potential as a short method to measure wanting in infants. Conclusion: The present study has demonstrated that the FIBFECS can be used to identify liking and wanting independent of subjective ratings from mothers and researchers, therefore, this tool can be used widely in the study of infant responses to novel foods at the time of weaning. There is potential to develop the tool for infants beyond the period of complementary feeding and to assist in identifying fussy eating in the early stages of development.

Developing a novel tool to assess liking and wanting in infants at the time of complementary feeding - The Feeding Infants : Behaviour and Facial Expression Coding System (FIBFECS)
Hetherington, M.M. ; Madrelle, J. ; Nekitsing, C. ; Barends, C. ; Graaf, C. de; Morgan, S. ; Parrott, H. ; Weenen, H. - \ 2016
Food Quality and Preference 48 (2016)Part A. - ISSN 0950-3293 - p. 238 - 250.
Complementary feeding - Facial expressions - Food refusal - Infant feeding - Like/dislike - Wanting - Weaning

Introduction: Consumption of foods is determined in part by how much a food is liked. However, assessing liking in infants is difficult. Research with infants has often relied on indirect measures such as intake or subjective ratings from mothers. Therefore the aim of the present research was to devise a tool adapted from existing techniques which can directly and systematically measure liking in infants during the weaning period. Method: A tool was developed by extracting items from previous studies. In all, 13 items were generated, which included 6 behaviours reflecting avoidance and approach: turning away, arching back, pushing spoon away, crying/fussy, leaning forward and rate of acceptance; also 7 facial expressions thought to reflect affective response; brow lowered, inner brow raised, squinting, nose wrinkling, upper lip raised, lip corners down and gaping. An e-training manual was developed with a certification test to train coders. The coding tool is based on coding the first 9 spoonfuls for each infant. 63 videos were coded by 4 raters, each video was coded by at least 2 different coders. For each spoonful the absence or presence of each item was recorded; for rate of acceptance, a four point scale was used. Results: In the certification test most cues were high in agreement for all coders. Factor analysis indicated two dimensions, one which largely captured gross behaviours and the second featuring a cluster of facial expressions. Internal consistencies of the overall scale and the behaviour and facial expression subscales were acceptable as indicated by Cronbach's alpha >0.7. Intra-class correlation indicated moderate to high inter-rater reliability and test-retest reliability for most of the cues. Spearman correlations indicated significant associations of the total number of negative behaviours with rate of acceptance and overall facial expressions. Rejection behaviours corresponded with a low rate of food acceptance and a high rate of negative facial expressions. Two parameters occurred less frequently and did not appear to provide any further discriminatory ability, namely leaning forward and crying/fussiness, these can be removed from the scale for future use. Conclusions: The Feeding Infants: Behaviour and Facial Expression Coding System (FIBFECS) is structurally valid and reliable for use by trained coders and those who are researching infant eating behaviour. The two factor structure of the tool suggests that the facial expression subscale reflects liking and the behaviour subscale wanting. The tool could also be adapted for mothers and professionals to detect liking and wanting through facial expression and behavioural cues respectively.

Vroeg boontjes proeven maakt nog geen groenteliefhebber
Barends, C. - \ 2015
Resource: weekblad voor Wageningen UR 9 (2015)21. - ISSN 1874-3625 - p. 9 - 9.
voedselconsumptie - baby's - groenten - voedingsgewoonten - food consumption - babies - vegetables - feeding habits
Baby’s die groente als eerste vast voedsel krijgen, eten hier als ze twee zijn, niet meer van dan andere kinderen. Op korte termijn zorgt gewenning wel voor meer groenteconsumptie. Dit concludeert Coraline Barends in haar proefschrift dat ze dinsdag 30 juni 2015 verdedigde.
'Mum, can I have Brussels sprouts again?’ : development of vegetable preferences during the first 2 years of life
Barends, C. - \ 2015
Wageningen University. Promotor(en): Kees de Graaf, co-promotor(en): Jeanne de Vries; Jos Mojet. - Wageningen : Wageningen University - ISBN 9789462573505 - 187
voedselvoorkeuren - voedselopname - zuigelingen - spenen - eten - smaakgevoeligheid - groenten - food preferences - food intake - infants - weaning - eating - taste sensitivity - vegetables

Abstract

Background and aim

Most children do not eat the recommended amount of vegetables. Their low vegetable intake may be attributed to their low preference for vegetables. Since the first years of life is a sensitive period in the development of taste preferences, and since taste preferences track over time, we started a longitudinal intervention study to investigate the effect of starting weaning with repeated exposure to vegetable purées on vegetable intake and liking during the first 2 years of life. The primary aim of this thesis was to investigate whether starting weaning with vegetables compared to weaning with fruit had an effect on the intake and liking of vegetables on the short and on the long term. The secondary aim was to investigate whether starting weaning with vegetables compared to weaning with fruit, influenced the preferences for sweet taste and daily intake of sugar.

Methods

First, we conducted an intervention study (n = 101) that investigated the effects of repeated exposure to either vegetable purées (vegetable groups) or fruit purées (fruit groups) on infants’ acceptance of vegetable or fruit purées during the first 18 days of weaning. Intake of the purées and mothers’ rated liking were measured in the lab. From a subsample (n = 60), we also measured liking by analysing the infants’ facial expressions and behaviour after consuming green beans purée in the lab. In two follow-up studies, when the infants were 12 (n = 84) and 23 months of age (n = 81), the long-term effect of the intervention was measured on intake and mothers’ rated liking of the purées in the lab. Additionally, infants’ daily vegetable intake was assessed with 3-day food records at both follow-ups. At the second follow-up, also the influence of starting with vegetables or fruits on children’s preferences for sweet and salty tastes (n = 81), were measured with sweetened and salted water solution and by calculating their daily mono- and disaccharides intake from the 3-day food records. Additionally, a systematic review investigated the current status of knowledge about effective strategies to increase vegetable intake in children younger than 3 y.

Results

The studies showed that the group of children who were repeatedly exposed to vegetables increased their vegetable intake from 24 ± 28 g to 45 ± 44g (p < 0.001), while the children who were repeatedly exposed to fruit increased their fruit intake from 46 ± 40 g to 66 ± 42 g (p < 0.05) . Interestingly, the first vegetable intake in the fruit group, which was directly after the 18 days of exposure to fruit purées, was as low as the first vegetable intake of the children in the vegetable group at day 1. This indicates that the repeated exposure to fruit did not influence the children’s vegetable intake. These results were confirmed by the results of the facial expressions, showing a decrease in negative facial expressions after repeated exposure to green beans.

At the follow-ups, when the infants were 12 and 23 months of age, no differences between the vegetable and fruit groups in green beans or apple purée were found in the lab. Daily intake of vegetables at 12 months of age, was 38% higher (p = 0.02) in the vegetable group (75 ± 43 g) than in the fruit group (54 ± 29 g). At 23 months of age, no significant difference in daily vegetable intake was found between the groups. Also the 23 month olds’ preference for sweet water solutions and their daily mono- and disaccharides intake did not differ between groups.

Finally, the systematic review of literature showed that counselling of the parents on healthy eating and nutrition did have a positive long-term effect on their children’s’ vegetable intake, although the effect was relatively small. The review further showed that repeated exposure was the most studied and also the most effective strategy, since all studies reported an increase in intake after repeated exposure to a vegetable. Also exposure to a variety of vegetables showed to have a positive effect on the intake of a new vegetable.

Conclusion

Weaning with repeated exposure to vegetables has a positive influence on vegetable intake until at least 12 months of age.

Effect of starting weaning exclusively with vegetables on vegetable intake at the age of 12 and 23 months
Barends, C. ; Vries, J.H.M. de; Mojet, J. ; Graaf, C. de - \ 2014
Appetite 81 (2014). - ISSN 0195-6663 - p. 193 - 199.
taste preferences - repeated exposure - food preferences - acceptance - children - fruit - infants - variety - consumption - adolescents
Background: The low vegetable intake in children may be attributed to their low preference for vegetables. During the first year of life, first taste preferences are formed, which may track over time. In a previous study to increase infants' vegetable intake and liking, we found that at the start of weaning, infants had a higher vegetable intake in the lab after repeated exposure to vegetable purées than to fruit purées. The current study is a follow-up of these infants at the age of 12 and 23¿months, and examined whether the group that started weaning with vegetables continued eating more vegetables than the group that started weaning with fruits. Methods: At 12 (n¿=¿86) and 23 (n¿=¿81) months of age the children's daily vegetable consumption was reported by their parents using a 3-day food diary. The intake of green beans and apple purée was measured in the laboratory. Results: Reported daily intake of vegetables at 12¿months of age was 38 % higher (P¿=¿0.02) in the vegetable group (75¿±¿43¿g) than in the fruit group (54¿±¿29¿g), but was similar for both groups at 23¿months of age (49¿±¿43, 57¿±¿35¿g, respectively; NS). Both at 12 and 23¿months of age, apple and green beans intake in the lab did not differ significantly between the groups. Conclusion: These findings suggest that weaning exclusively with vegetables results in a higher daily vegetable consumption until at least 12¿months of age. More research is needed to investigate how to maintain this effect.
A technical investigation on tools and concepts for sustainable management of the subsurface in The Netherlands.
Griffioen, J. ; Wensem, J. van; Oomes, J.L. ; Barends, F. ; Breunese, J. ; Bruining, H. ; Olsthoorn, T. ; Stams, A.J.M. ; Stoel, A.E. van der - \ 2014
Science of the Total Environment 485-486 (2014). - ISSN 0048-9697 - p. 810 - 819.
risk-assessment - groundwater sustainability - resources management - decision-making - mining-industry - european-union - water - storage - policy - framework
In response to increasing use of the subsurface, there is a need to modernise policies on sustainable use of the subsurface. This holds in particular for the densely populated Netherlands. We aimed to analyse current practice of subsurface management and the associated pressure points and to establish a conceptual overview of the technical issues related to sustainable management of the subsurface. Case studies on the exploitation of subsurface resources (including spatial use of the subsurface) were analysed, examining social relevance, environmental impact, pressure points and management solutions. The case studies ranged from constructing underground garages to geothermal exploitation. The following issues were identified for the technological/scientific aspects: site investigation, suitability, risk assessment, monitoring and measures in the event of failure. Additionally, the following general issues were identified for the administrative aspects: spatial planning, option assessment, precaution, transparency, responsibility and liability. These issues were explored on their technological implications within the framework of sustainable management of the subsurface. This resulted into the following key aspects: (1) sustainability assessment, (2) dealing with uncertainty and (3) policy instruments and governance. For all three aspects, different options were identified which might have a legal, economic or ethical background. The technological implications of these backgrounds have been identified. A set of recommendations for sustainable management of the subsurface resources (incl. space) was established: (1) management should be driven by scarcity, (2) always implement closed loop monitoring when the subsurface activities are high-risk, (3) when dealing with unknown features and heterogeneity, apply the precautionary principle, (4) responsibility and liability for damage must be set out in legislation and (5) sustainability should be incorporated in all relevant legislation and not only in environmental legislation. Other aspects to be considered are the reversibility of the impacts from subsurface activities and the abandonment of installations.
Effects of repeated exposure to either vegetables or fruits on infant's vegetable and fruit acceptance at the beginning of weaning
Barends, C. ; Vries, J. de; Mojet, J. ; Graaf, C. de - \ 2013
Food Quality and Preference 29 (2013)2. - ISSN 0950-3293 - p. 157 - 165.
developmental-changes - food preferences - variety - children - life - experience - formula
This study investigated the effects of repeated exposure to either vegetables or fruits on an infant's vegetable and fruit acceptance during the first 18 days of weaning. We hypothesized that repeated exposure to a type of vegetable or fruit, would increase its intake. Furthermore, we expected that being exclusively weaned with vegetables would result in a higher acceptance of vegetables than being exclusively weaned with fruits. To investigate this, a 19-day intervention study was conducted in 101 healthy infants, aged 4-6 months. Infants were randomly assigned to one of four treatment groups. Two groups received exclusively vegetable purees as targets every other day for 18 consecutive days; green beans was the target for one group and artichoke for the other group. The other two groups received exclusively fruit purees including either apple or plums as the target fruit. On day 19, the vegetable groups consumed their first fruit pur e and the fruit groups their first vegetable pur e. At the beginning of the study on days 1 and 2 and at the end on days 17, 18 and 19, the infants were fed fruit or vegetable pur e in our laboratory. On days 3-16, the parents fed their infants the fruit or vegetable purees at home. Outcome variables were vegetable and fruit intake over time. Mean vegetable intake in the vegetable group increased significantly from 24 28 g (mean +/- SD) on days 1 and 2 to 45 +/- 44 g on days 17 and 18. Fruit intake in the fruit group increased significantly from 46 +/- 40 to 66 +/- 42 g. Fruit intake was significantly higher than vegetable intake from the start. Repeated exposure to fruit had no effect on the vegetable intake. The first intake of green beans in the fruit groups at day 19, was 24 +/- 29 g and on average as low as the green beans intake in the vegetable groups at the 1st exposure on days 1 or 2. Similarly, the first apple intake in the fruit groups on days 1 or 2 of 47 +/- 48 g did on average not differ from the first apple intake of 45 +/- 49 g in the vegetable groups on day 19. The mean intake of green beans and plums increased significantly after repeated exposure. The intake of the target food artichoke stayed low and the intake of apple only increased slightly. These findings confirm that at the first exposure fruit acceptance is higher than vegetable acceptance. Weaning with vegetables, but not with fruits, may promote vegetable acceptance in infants. (C) 2013 Elsevier Ltd. All rights reserved.
Enhanced production of Aspergillus niger laccase-like multicopper oxidases through mRNA optimization of the glucoamylase expression system
Tamayo Ramos, J.A. ; Barends, S. ; Lange, D. ; Jel, A. de; Verhaert, R.M. ; Graaff, L.H. de - \ 2013
Biotechnology and Bioengineering 110 (2013)2. - ISSN 0006-3592 - p. 543 - 551.
5'-untranslated region - protein expression - gene - translation - transformation - promoter - nidulans - cloning - oryzae
In filamentous fungi, most of the strategies used for the improvement of protein yields have been based on an increase in the transcript levels of a target gene. Strategies focusing at the translational level have been also described, but are far less explored. Here the 5' untranslated sequence of the glaA mRNA, a widely used expression system for the expression of recombinant proteins, was modified by the introduction of different nucleotide elements that have positive role in the translation process. Five Aspergillus niger laccase-like multicopper oxidases (MCOs) coding genes were fused to the native glaA 5'UTR and the three synthetic versions (sUTR1, sUTR2, and sUTR3) as well, and placed under the control of the glucoamylase gene promoter. Afterwards, a total of 20 fungal transformations were done using A. niger N593 as a recipient strain and 50 transformants per transformation were isolated and analyzed. The result of the incorporation of the synthetic 5'UTRs on the overall productivity of the transformants was assessed, on one hand by monitoring the laccase activity of all the isolated transformants, and on the other hand by quantifying and comparing the activity of those secreting the highest level of each MCO. For this purpose, a high-throughput method for the screening and selection of the best producers was developed. Once the best transformants producing the highest yield of McoA, McoB, McoC, McoD, and McoJ laccases were selected, their production level was quantified in supernatants of liquid cultures. The results obtained in this work indicate that modifications in the native glaA 5'UTR can lead to improvements in protein yields. Biotechnol. Bioeng. © 2012 Wiley Periodicals, Inc
The Aspergillus niger multicopper oxidase family: analysis and overexpression of laccase-like encoding genes
Tamayo Ramos, J.A. ; Barends, S. ; Verhaert, R.M. ; Graaff, L.H. de - \ 2011
Microbial Cell Factories 10 (2011). - ISSN 1475-2859 - p. 78 - 78.
heterologous expression - recombinant enzyme - saccharomyces-cerevisiae - melanocarpus-albomyces - secreted proteins - filamentous fungi - multigene family - nidulans - fumigatus - sequence
BACKGROUND: Many filamentous fungal genomes contain complex groups of multicopper oxidase (MCO) coding genes that makes them a good source for new laccases with potential biotechnological interest. A bioinformatics analysis of the Aspergillus niger ATCC 1015 genome resulted in the identification of thirteen MCO genes. Ten of them were cloned and homologously overexpressed. RESULTS: A bioinformatic analysis of the A. niger ATCC 1015 genome revealed the presence of 13 MCO genes belonging to three different subfamilies on the basis of their phylogenetic relationships: ascomycete laccases, fungal pigment MCOs and fungal ferroxidases. According to in silico amino acid sequence analysis, the putative genes encoding for functional extracellular laccases (mcoA, mcoB, mcoC, mcoD, mcoE, mcoF, mcoG, mcoI, mcoJ and mcoM) were placed under the control of the glaA promoter and overexpressed in A. niger N593. Enzyme activity plate assays with several common laccase substrates showed that all genes are actually expressed and code for active MCOs. Interestingly, expressed enzymes show different substrate specificities. In addition, optimization of fungal pigment MCOs extracellular production was investigated. The performance of the widely used glucoamylase signal sequence (ssGlaA) in McoA secretion was studied. Results obtained suggest that ssGlaA do not yield higher levels of secreted McoA when compared to its native secretion signal. Also, McoB synthesis was investigated using different nitrogen sources in minimal medium liquid cultures. Higher yields of extracellular McoB were achieved with (NH4)2 tartrate. CONCLUSIONS: Aspergillus niger is a good source of new laccases. The different substrate specificity observed in plate assays makes them interesting to be purified and biochemically compared. The homologous signal sequence of McoA has been shown to be a good choice for its extracellular overexpression. From the nitrogen sources tested (NH4)2 tartrate has been found to be the most appropriate for McoB production in A. niger
Structural insight into substrate binding and catalysis of a novel 2-keto-3-deoxy-D-arabinonate dehydratase illustrates common mechanistic features of the FAH superfamily
Brouns, S.J.J. ; Barends, T.R.M. ; Worm, P. ; Akerboom, J. ; Turnbull, A.P. ; Salmon, L. ; Oost, J. van der - \ 2008
Journal of Molecular Biology 379 (2008)2. - ISSN 0022-2836 - p. 357 - 371.
l-arabinose metabolism - alpha-ketoglutaric semialdehyde - fumarylacetoacetate hydrolase - crystal-structure - escherichia-coli - caulobacter-crescentus - alternative pathway - l-2-keto-3-deoxyarabonate dehydratase - evolutionary insight - d-xylose
The archaeon Sulfolobus solfataricus converts d-arabinose to 2-oxoglutarate by an enzyme set consisting of two dehydrogenases and two dehydratases. The third step of the pathway is catalyzed by a novel 2-keto-3-deoxy-D-arabinonate dehydratase (KdaD). In this study, the crystal structure of the enzyme has been solved to 2.1 A resolution. The enzyme forms an oval-shaped ring of four subunits, each consisting of an N-terminal domain with a four-stranded beta-sheet flanked by two alpha-helices, and a C-terminal catalytic domain with a fumarylacetoacetate hydrolase (FAH) fold. Crystal structures of complexes of the enzyme with magnesium or calcium ions and either a substrate analog 2-oxobutyrate, or the aldehyde enzyme product 2,5-dioxopentanoate revealed that the divalent metal ion in the active site is coordinated octahedrally by three conserved carboxylate residues, a water molecule, and both the carboxylate and the oxo groups of the substrate molecule. An enzymatic mechanism for base-catalyzed dehydration is proposed on the basis of the binding mode of the substrate to the metal ion, which suggests that the enzyme enhances the acidity of the protons alpha to the carbonyl group, facilitating their abstraction by glutamate 114. A comprehensive structural comparison of members of the FAH superfamily is presented and their evolution is discussed, providing a basis for functional investigations of this largely unexplored protein superfamily.
Zandlandschap
Vervloet, J.A.J. - \ 2000
In: Het Nederlandse landschap; een historisch-geografische benadering; 8e herz. druk / Barends, S., Baas, H.G., de Harde, M.J., Renes, J., Stol, T., van Triest, J.C., de Vries, R.J., van Woudenberg, F.J., Utrecht : Matrijs - p. 104 - 127.
Voedingsmiddelen en Consumentengedrag
Verlegh, P.W.J. ; Rekom, J. van - \ 2000
In: Praktijkhandboek Voedselveiligheid / Barends, T., Amsterdam : Weka Publishers - p. 310.01 - 310.10.
Monitoring the effects of subsidence of the coastal island Ameland in the Wadden Sea
Eysink, W.D. ; Hug, P. ; Dijkema, K.S. ; Smit, C.J. ; Dobben, H.F. van - \ 1995
In: In; F.B.J. Barends, F.J.J. Brouwer & F.H. Schroder (eds.), Proceedings fifth international symposium on land subsidence; The Hague, 16-20 October 1995, Balkema, Rotterdam; 259-267
Natuurbeleidsplan project 33a : ontwikkeling van een inventarisatiemethode en een GIS voor cultuurhistorische landschapselementen en waardevolle gebieden
Barends, S. - \ 1993
Wageningen etc. : DLO-Staring Centrum [etc.] (Rapport / DLO-Staring Centrum 262) - 121
classificatie - computers - gegevensverwerking - descriptoren - geografische informatiesystemen - geografie - identificatie - landschap - microcomputers - minicomputers - nederland - machines - classification - data processing - descriptors - geographical information systems - geography - identification - landscape - netherlands
Doolhof : dwalen als vermaak
Oldenburger - Ebbers, C.S. - \ 1993
In: Over hagelkruisen, banpalen en pestbosjes : historische landschapselemmenten in Nederland / Barends, S., Renes, H., Stol, T., Utrecht : Matrijs - p. 112 - 113.
Typologie op basis van historisch-geografische karakteristieken van het landschap : eindverslag van het tweede gedeelte van het onderzoeksproject
Barends, S. - \ 1992
Wageningen : DLO-Staring Centrum (Rapport / DLO-Staring Centrum 141) - 147
landbouwgrond - landschap - nederland - velden - historische geografie - verkaveling - agricultural land - landscape - netherlands - fields - historical geography - land parcelling
Het zandlandschap.
Vervloet, J.A.J. - \ 1991
In: Het Nederlandse landschap. Een historisch-geografische benadering / Barends, S., Utrecht : - p. 9 - 26.
Versnippering van het landschap : historisch-geografische benadering van versnippering
Barends, S. - \ 1989
Wageningen : Stichting voor Bodemkartering (Rapport / Stichting voor Bodemkartering nr. 2078) - 123
landschap - cultuurlandschap - historische geografie - fragmentatie - landscape - cultural landscape - historical geography - fragmentation
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