Crystals, glasses and gels : synthesis and phase behavior of soft colloids
Appel, Jeroen - \ 2017
Wageningen University. Promotor(en): Frans Leermakers, co-promotor(en): Joris Sprakel. - Wageningen : Wageningen University - ISBN 9789463430104 - 139
colloids - crystals - gels - phases - physics - colloidal properties - physical chemistry - colloïden - kristallen - gels - fasen (chemie) - fysica - colloïdale eigenschappen - fysische chemie
Colloidal suspensions are an experimental model system for studying structural and mechanical properties of soft materials. These properties are manifested differently in colloidal solid-like phases such as crystals, glasses and gels. To further understand relations between structural and mechanical properties, it is necessary to develop well-defined colloids and employ techniques such as microscopy and rheology to study the structure and mechanics of their suspensions. This thesis presents five experimental chapters dealing with the synthesis and characterization of colloids and their suspensions. The first part of the thesis describes facile synthesis methods for latex, conjugated polymer and microgel colloids. In the second part, measurements of crystal-to-glass and glass-to-gel phase transformations in dense suspensions of microgel particles are presented.
Toeval en toedracht : over gebeurtenissen in de Fysische Chemie
Cohen Stuart, M.A. - \ 2013
Wageningen : Wageningen University, Wageningen UR - ISBN 9789461736154 - 23
fysische chemie - oorzakelijkheid - physical chemistry - causality
Rede bij het afscheid als hoogleraar in Fysische Chemie en Kolloidkunde aan Wageningen University op 25 april 2013.
Brushes and particles
Vos, W.M. de - \ 2009
Wageningen University. Promotor(en): Martien Cohen Stuart, co-promotor(en): Arie de Keizer; Mieke Kleijn. - [S.l. : S.n. - ISBN 9789085854524 - 264
polymeren - oppervlaktespanningsverlagende stoffen - oppervlakte-interacties - fysische chemie - polymers - surfactants - surface interactions - physical chemistry
Chain stoppers in reversible supramolecular polymer solutions
Knoben, W. - \ 2007
Wageningen University. Promotor(en): Martien Cohen Stuart, co-promotor(en): N.A.M. Besseling. - [S.l.] : s.n. - ISBN 9789085045748 - 194
polymeren - polymerisatie - fysische chemie - fysicochemische eigenschappen - supramoleculaire chemie - polymers - polymerization - physical chemistry - physicochemical properties - supramolecular chemistry - cum laude
cum laude graduation (with distinction)
Het zijn de kleine dingen die het doen
Norde, W. - \ 2006
Wageningen : Wageningen Universiteit - 36
fysische chemie - microscopie - micellen - biotechnologie - nanotechnologie - physical chemistry - microscopy - micelles - biotechnology - nanotechnology
|Physical chemistry of foods
Walstra, P. - \ 2003
New York [etc.] : Marcel Dekker (Food science and technology 121) - ISBN 9780824793555 - 807
fysische chemie - fysische eigenschappen - voedsel - fysica - voedselchemie - voedselwetenschappen - studieboeken - physical chemistry - physical properties - food - physics - food chemistry - food sciences - textbooks
Exploring the structure and physical and chemical properties of solutions, dispersions, soft solids, fats, and cellular systems, this text describes the physicochemical principles essential to the comprehension and prediction of reactions and conversions that occur during the manufacture, handling, and storage of foods. The book contains practical examples of starch gelatinization and retrogradation, protein denaturation, lipid crystallization, foam and emulsion formation, colloidal interactions, glass transitions, and food freezing and structure, etc.
Scenario Studies into Advanced Particle Removal in the Physical-Chemical Pre-treatment of Wastewater
Nieuwenhuijzen, A.F. van - \ 2002
Delft : DUP Science - ISBN 9789040722493 - 256
afvalwaterbehandeling - voorbehandeling - fysische chemie - duurzaamheid (sustainability) - deeltjes - waste water treatment - pretreatment - physical chemistry - sustainability - particles
Chemical enhanced pre-treatment of wastewater in The Netherlands - Treating wastewater the Scandinavian way in The Netherlands
Nieuwenhuijzen, A.F. van; Mels, A.R. ; Gerhardt-Meilink, P.H. - \ 2001
European water management : official publication of the European Water Pollution Control Association 4 (2001)4. - ISSN 1461-6971 - p. 43 - 46.
afvalwaterbehandeling - waterzuivering - voorbehandeling - fysische chemie - biologische behandeling - scandinavië - nederland - waste water treatment - water treatment - pretreatment - physical chemistry - biological treatment - scandinavia - netherlands
Direct influent filtration as a pretreatment step for more sustainable wastewater treatment systems.
Nieuwenhuijzen, A.F. van; Graaf, J.H.J.M. van der; Mels, A.R. - \ 2001
Water Science and Technology 43 (2001)11. - ISSN 0273-1223 - p. 91 - 98.
afvalwaterbehandeling - voorbehandeling - fysische chemie - filtratie - deeltjes - verwijdering - duurzaamheid (sustainability) - nederland - waste water treatment - pretreatment - physical chemistry - filtration - particles - removal - sustainability - netherlands
Beheer van organische stof in open biologische, ecologische en geïntegreerde teeltsystemen
Zwart, K.B. ; Whitmore, A.P. ; Bokhorst, J.G. - \ 1999
Wageningen : AB-DLO - 90
organische verbindingen - fysische chemie - bodem - mineralisatie - bedrijfssystemen - alternatieve landbouw - biologische landbouw - geïntegreerde bedrijfssystemen - organic compounds - physical chemistry - soil - mineralization - farming systems - alternative farming - organic farming - integrated farming systems
Linden, E. van der - \ 1999
Wageningen : Wageningen Universiteit - 22
fysica - fysische chemie - voedsel - voedselwetenschappen - voedselchemie - physics - physical chemistry - food - food sciences - food chemistry
Physical quality of pelleted feed : a feed model study
Thomas, M. - \ 1998
Agricultural University. Promotor(en): M.W.A. Verstegen; S. Tamminga; A.F.B. van der Poel. - S.l. : Thomas - ISBN 9789054858720 - 263
korrelvoer - voer - kwaliteitscontroles - fysica - mechanica - temperatuur - fysische chemie - samenstelling - voedermiddelbewerking - pelleted feeds - feeds - quality controls - physics - mechanics - temperature - physical chemistry - composition - feed processing
In this study, a review and experimental work is presented on the relation between processing conditions and functional properties of feed constituents with respect to hardness and durability characteristics of pelleted feed. In the first three chapters, a literature overview is presented which describes the methodologies used to determine hardness and durability characteristics of pelleted feed. The second article deals with the effects of processing conditions on the physical quality of pelleted feed. In the last review, article an overview is presented on the effect of raw material constituents and pellet quality.
The effects of processing conditions on changes in starch degree of gelatinization of tapioca meal and protein quality of soy grits (as two model feeds) have been studied. It was concluded that addition of steam and water had a larger effect on changes in the starch degree of gelatinization and the denaturation of protein than the amount of dissipated mechanical energy. Hardness and durability characteristics of pelleted feed were influenced by the amount of dissipated mechanical energy and the amount of steam used.
Mixture studies were conducted in which the state of the model feed constituents -starch and protein- was altered and the subsequent effects on pellet hardness and durability were studied. From these studies it was concluded that an increase in the degree of gelatinization, or an increase in the amount of native protein leads to harder and more durable pellets. Possible explanations for these effects such as the change in deformability of the particles that make up the feed mash and the ability of the starch or protein to act as a binder, are described.
Econatuurkunde oftewel De entropie van het gazon.
Lyklema, J. - \ 1995
Wageningen : Landbouwuniversiteit Wageningen - 33
ecologie - colleges (hoorcolleges) - fysische chemie - fysiologie - ecofysiologie - ecology - lectures - physical chemistry - physiology - ecophysiology
Walstra, P. ; Vliet, T. van - \ 1995
Industrial Proteins 2 (1995)1. - ISSN 1381-0022 - p. 3 - 5.
gelering - fysische chemie - eiwitten - fysicochemische eigenschappen - reologische eigenschappen - gels - suspensies - gelation - physical chemistry - proteins - physicochemical properties - rheological properties - gels - suspensions
Het geven van een gewenste consistentie of van een bepaalde vaste vorm aan eiwitbevattende mengsels komt in het algemeen neer op het doen geleren van het eiwit. De vraag welke soorten reologische eigenschappen dan nodig zijn wordt kort besproken. Daarna komen de drie voornaamste typen eiwitgelen aan de orde, te weten gelatine, deeltjesgelen (bijvoorbeeld van caseïnedeeltjes) en gelen gevormd als gevolg van hittedenaturatie van globulaire eiwitten (bijvoorbeeld van ovalbumine, ß-lactoglobuline, sommige vleeseiwitten). Deze typen verschillen nogal in vormingswijze en in eigenschappen
Statistical thermodynamics of fluids with orientation - dependent interactions : applications to water in homogeneous and heterogeneous systems
Besseling, N.A.M. - \ 1993
Agricultural University. Promotor(en): J. Lyklema; J.M.H.M. Scheutjens. - S.l. : Besseling - ISBN 9789054851516 - 225
water - eigenschappen - fysische chemie - vloeistoffen (liquids) - gassen - thermodynamica - chemie - vaste stoffen - water - properties - physical chemistry - liquids - gases - thermodynamics - chemistry - solids - cum laude
The aim of the present study was to develop a lattice theory for systems, homogeneous as well as heterogeneous, containing molecules with orientation- dependent interactions such as water. It was soon recognised that the so-called Bragg-Williams mean-field approximation is not capable of reproducing the typical temperature dependence of the thermodynamic properties of such systems. This is due to the neglect of correlations between positions and orientations of the molecules. To improve this, we based ourselves on the so called quasi-chemical approximation.
In chapter I , some background information is given on the systems with which the present study is concerned and the theoretical methods that are employed.
In chapter II the theory is derived in a general fashion, for an arbitrary collection of monomeric species. To model heterogeneous systems, the lattice is divided into parallel layers. The density of each monomeric species and the orientational distribution are allowed to be different for each layer. A partition function is derived as a sum over distributions of molecules over orientations and positions and over distributions of intermolecular contacts. From this, self- consistent field equations are obtained for the equilibrium distributions. Further, it is indicated how free-volume effects can be accounted for by allowing sites to be vacant. Expressions are obtained for energy, entropy, chemical potentials, pressure and surface tension etc..
The self-consistent field equations are solved numerically by means of a modified Newton iteration. A major complication in the numerical problem associated with this theory is the necessity to simultaneously iterate the density distribution of the various molecular orientations as well as the distribution of contacts between molecules. With selfconsistent field theories that are based on the Bragg-Williams approximation such as that of Scheutjens and Fleer, the distribution of contacts is simply assumed to be random, even if there are non-zero interactions.
At the end of chapter II, the capabilities of the method are illustrated by applying it to a number of specific systems containing molecules with orientation-dependent interactions. The coexistence curves that are calculated show that orientation-dependent interactions can give rise to an increasing solubility with decreasing temperature. Also for the interfacial properties the orientation- dependent nature of the intermolecular interactions is shown to be of great importance. For special model systems it is found that the tension of the interface between coexisting phases increases with increasing temperature. Of a system that exhibits a closed-loop coexistence curve, the interfacial tension of the interface between the coexisting phases vanishes at the lower critical solution temperature. Upon increasing temperature it increases, passes a maximum and decreases until it vanishes again at the upper critical solution temperature. The structural differences at the interface between temperatures at which the interfacial entropy is negative and where it is positive are discussed.
Chapters III to VI are concerned with various properties of water.
In chapter III , a lattice-gas model for water is introduced that is elaborated by the formalism of chapter II. This theory appeared to be capable of reproducing various anomalous thermodynamic properties of water. The calculated equation of state and liquid-vapour phase diagram agree at least qualitatively with the experimental behaviour of water. For instance, the maximum of the isobaric density as a function of temperature is reproduced. Within this model it is possible to analyse the relation between macroscopic behaviour and the microscopic structure of liquid water. The amount of intact hydrogen bonds can be calculated as well as that of the other intermolecular contacts. Over a large range of temperatures and densities, the fraction of intact hydrogen-bonds is close to unity. This confirms that liquid water can be considered as a percolating hydrogen-bonded network.
The liquid-vapour interface is also investigated. A salient result is the increase of the interfacial thickness and the density-coherence length of liquid water upon decreasing temperature. This result still awaits experimental verification. Further, the minimum of the temperature coefficient of the interfacial tension as a function of temperature is reproduced by the theory.
In chapter IV the so-called hydrophobic effect is addressed. It is made plausible that the physics underlying the anomalous thermodynamics of solvation by water of small apolar molecules is similar to that of the isobaric density maximum of pure water. An explanation is given for the exothermic solvation of apolar compounds below room temperature. This is attributed to a decrease of repulsive non-hydrogen bonding interactions between water molecules. The large entropy effect of solvating apolar compounds is also reproduced by the theory. For the explanation of these phenomena it appears to be unnecessary to invoke so-called iceberg formation around apolar molecules. Another interesting result is that the solvation thermodynamics of small molecules and of extended surfaces appears to be very different.
In chapter V , hydration forces, water-structure mediated forces between surfaces, are the main subject. There is experimental evidence for the occurrence of such forces in systems as different as biological membranes and inorganic colloids. Both within a phenomenological approach based on a Landau expansion of the free-energy density as in results from the lattice-theory, it is found that these forces can be attractive or repulsive, depending on the properties of the surfaces. More specifically, the sign of the interaction depends on the type of ordering induced by the surfaces in adjoining water. If the solvation layers of two surfaces overlap in such a way that the ordering is enhanced, the ensuing interaction between the surfaces is attractive. This indicates that the accepted view, that the water-structure mediated interaction between hydrophilic surfaces is always repulsive, needs reconsideration. If the structuring is distorted by overlap, then a repulsive force is the result.
Chapter VI contains some preliminary results on vapour adsorption and on wetting phenomena. For various model surfaces and temperatures vapour- adsorption isotherms are calculated. In this way, the understanding of the relation between the properties of surfaces and the adsorption of water vapour is improved. For a number of surfaces a transition from partial wetting to complete wetting is found with variation of the properties of the surface or of temperature. The interfacial tension of the solid-vapour and the solid-liquid interface at the saturation pressure has been calculated, as well as that of the liquid-vapour interface. Consequently, using Young's law, the contact angle can be obtained together with related quantities such as the reversible work of adhesion and the spreading coefficient.
In chapter VII , the formalism of chapter II is extended towards systems containing chain molecules. Such molecules consist of segments, each occupying one lattice site. Generally, they can have a large number of conformations. It is indicated how the (semi)flexibility of chain molecules can be accounted for within the theory. Correlations due to the connected nature of segments are accounted for in firstorder approximation. This is consistent with the way correlations due to energetic interactions are accounted for. It has been possible to derive a recurrence relation for the statistical weight of chains of different lengths which allows an efficient evaluation of the statistical weight of each possible chain conformation.
Conformation of the RNA-binding N-terminus of the coat protein of cowpea chlorotic mottle virus : a nuclear magnetic resonance and optical spectroscopy study
Graaf, M. van der - \ 1992
Agricultural University. Promotor(en): T.J. Schaafsma; M.A. Hemminga. - S.l. : Van der Graaf - 113
koebonenmozaïekvirus - virologie - moleculaire biologie - fysische chemie - fysica - eiwitten - spectroscopie - spectraalanalyse - analytische methoden - rna - kernmagnetische resonantie - kernmagnetische resonantiespectroscopie - optica - cowpea mosaic virus - virology - molecular biology - physical chemistry - physics - proteins - spectroscopy - spectral analysis - analytical methods - rna - nuclear magnetic resonance - nuclear magnetic resonance spectroscopy - optics
The objective of the study described in this thesis was to obtain information about protein-RNA interactions in cowpea chlorotic mottle virus (CCMV). CCMV consists of RNA and a protective protein coat, composed of 180 identical coat proteins. The positively charged N-terminal arm of the coat protein is essential for binding the encapsidated RNA. Previously, the so-called 'snatch-pull' model has been suggested for the assembly of coat protein and RNA. According to this model the N-terminal region has a flexible random-coil conformation in the absence of RNA, but attains an a-helical conformation upon RNA-binding. In the present study a synthetic peptide containing the first 25 amino acids of CCMV coat protein (P25) was used as a model for the N- terminus, and oligophosphates and oligonucleoticles were used as models for the viral RNA. The conformation of the peptide was studied by nuclear magnetic resonance (NMR) and circular dichroism (CID). Changes in the conformation of the oligonucleotides were studied by CD and absorbance spectroscopy. The results confirm the snatch-pull model and allow an extension to a more detailed model for the assembly of CCMV coat protein and RNA (see below).
Chapter 2 describes the effects of ionic strength, addition of (oligo) phosphates, and temperature on the conformation of the peptide P25 containing six arginines and three lysines. CD experiments show that the peptide has 15-18% α-helical and about 80% random coil conformation in the absence of inorganic salt at 25°C. Lowering the temperature to 10°C increases the a-helix content to 20-21%. Addition of inorganic salts results in a larger increase of the amount of α-helical conformation, up to 42% in the presence of oligophosphate with an average chain length of eighteen phosphates. One-dimensional proton NMR experiments show that the α-helix formation starts in the region between Thr9 and GIn12, and is extended in the direction of the C-terminus. NMR relaxation measurements show that binding to oligophosphates of increasing length results in reduced internal mobilities of the positively charged side chains of the arginyl and lysyl residues and of the side chain of Thr9 at the beginning of the α-helical region.
Chapter 3 gives a description of two-dimensional proton NMR experiments on P25 in the presence of sodium monophosphate. All resonances could be assigned by a combined use of two-dimensional correlated spectroscopy and nuclear Overhauser enhancement spectroscopy carried out at four different temperatures. Various NMR parameters indicate the presence of a conformational ensemble consisting of helical structures rapidly interconverting to more extended states. Differences in chemical shifts and nuclear Overhauser effects indicate that lowering the temperature induces a shift of the dynamic equilibrium towards the helical structures. At 10°C a perceptible fraction of the conformational ensemble consists of structures with an a-helical conformation between residues 9 and 17, likely starting with a turn- like structure around Thr9 and Arg10. The region close to Arg 10 shows the strongest tendency to attain an α-helical conformation.
Chapter 4 presents a two-dimensional proton NMR study on the effect of (oligo)phosphates on the conformation of P25. NMR experiments were performed on the highly positively charged peptide in the presence of an excess of monophosphate, tetraphosphate or octadecaphosphate. The peptide alternates between various extended and helical structures in the presence of monophosphate, but this equilibrium shifts towards the helical structures in the presence of oligophosphates. In the presence of tetraphosphate the α-helical region is situated between residues 10 and 20. NMR distance constraints obtained for P25 in the presence of tetraphosphate have been used to generate peptide structures by distance geometry calculations. These calculations resulted in eight structures belonging to two structure families. The first family consists of five structures with an α-helix-like conformation in the middle of the peptide, and the second family consists of three structures with a more open conformation. The presence of two structure families indicates that even in the presence of tetraphosphate the peptide is flexible.
Chapter 5 describes a two-dimensional proton NMR study on the intact coat protein of cowpea chlorotic mottle virus (molecular mass: 20.2 kDa) present as dimer (pH = 7.5) or as capsid consisting of 180 protein monomers (pH = 5.0). The spectra of both dimers and capsids show resonances originating from the flexible N-terminal region of the protein. The complete resonance assignment of P25 made it possible to interpret the spectra in detail. The capsid spectrum shows backbone amide proton resonances arising from the first eight residues having a flexible random coil conformation, and side- chain resonances arising from the first 25 N-terminal amino acids. The dimer spectrum shows also side-chain resonances of residues 26 to 33, which are flexible in the dimer but immobilized in the capsid. It is suggested that the carboxyl group of GIu33 plays a role in the pH-dependent association of the coat protein. Neutralization of this acidic residue by low pH or by the presence of positively charged bases of the RNA possibly results in a conformation necessary for capsid formation. The NMR experiments indicate that the conformation of the first 25 amino acids of the intact viral coat protein in dimers and capsids is comparable to the conformation of the synthetic peptide P25.
Finally, Chapter 6 deals with the effect of P25 on the structure of oligonucleoticles. The experiments described in this chapter have been carried out on samples containing micromolar concentrations of both P25 and oligonucleoticles. For NMR measurements samples with concentrations of more than 100 times higher are necessary. Unfortunately, it was not possible to avoid precipitation at such high concentrations of P25 and oligonucleotides in aqueous solution. However, conformational changes of the oligonuclecitides r(A) 12 , d(GC) , and d(AT) 5 upon binding to P25 could be studied by using absorption and CD spectroscopy. r(A) 12 has a single-stranded structure at pH = 7.2, and exists as a protonated duplex at pH-values below 5.8. In this duplex a phosphate oxygen of the RNA backbone forms a hydrogen bond to the amino group of the adenine. The oligonucleoticles d(GC) 5 and d(AT) 12 form duplexes with Watson-Crick base-pairing. The results show that P25 has only a minor effect on the single-stranded structure of r(A) 12 at pH 7.2, but disrupts the double-stranded structure of r(A) 12 at pH = 5.0. At pH = 4.0, the double stranded structure of r(A) 12 is stabilized by protonation of the adenine at the N 1 position and the peptide is not able to disrupt the double-stranded structure. The double-stranded structures of d(GC) 5 and d(AT) 5 with Watson-Crick base-pairing are stabilized upon binding to the peptide. All conformational changes observed indicate that the positively charged side chains of the peptide have strong electrostatic interactions with the negatively charged phosphate groups of the oligonucleoticles.
The results of the study described in this thesis confirm the snatch-pull model mentioned in the beginning of this summary. Although P25 alternates between various conformations in aqueous solution, the region between residues 10 and 20 shows a tendency to adopt an α-helical conformation. This α-helical structure is stabilized by low temperature, high ionic strength, and the addition of (oligo)phosphates, mimicking the RNA. It has been shown that the α-helix formation starts in the region between Thr9 and GIn12. Based upon this observation, a more detailed model for the assembly of CCMV coat protein and the viral RNA is proposed. It is suggested that hydrogen bond formation by the side chains of Thr9 and GIn12 initiates α-helix formation. After this initiation, the helix is extended in the direction of the C-terminus upon binding of negatively charged phosphate groups to the positively charged side chains present in the N-terminal region of the coat protein. The results indicate a strong effect of the presence of phosphates on Arg10. Phosphate binding to this residue may extend the helix in the direction of the C-terminus because of the removal of an unfavourable interaction between the positive charge at this position and the macrodipole of the helix. The extension of the helical region results in a proper orientation of the positively charged side chains for binding to the phosphate groups of the RNA backbone. In an alfa- helical conformation the distance between the arginines at positions 10, 14, 18 and 22 (- 6 Å) is comparable to the distance between two neighbouring phosphate groups in an A-type RNA helix (- 5.9 Å).
Een poging de door micro-organismen gemakkelijk ontleedbare organische stof in grond te bepalen : met bijlage : bepaling van organische koolstof in waterige (zout)oplossingen
Bruins, E.H. - \ 1980
Haren : Instituut voor Bodemvruchtbaarheid (Rapport / Instituut voor Bodemvruchtbaarheid no. 9-80) - 24
koolhydraten - koolstof - cellulose - decompositie - organische stof - fysische chemie - bodem - bodemchemie - carbohydrates - carbon - cellulose - decomposition - organic matter - physical chemistry - soil - soil chemistry
Een fysico - chemicus aan het werk
Lyklema, J. - \ 1963
Wageningen : Unknown Publisher - 16
fysische chemie - openbare redes - physical chemistry - public speeches
A spherical radiation meter
Wassink, E.C. ; Scheer, C. van der - \ 1951
Wageningen : [s.n.] (Mededelingen / Landbouw Hogeschool Dl. 51, no. 9) - 10
fysische chemie - physical chemistry
Localisaties op grensvlakken
Tendeloo, H.J.C. - \ 1931
Wageningen : Veenman - 19
oppervlakte-interacties - colloïdale eigenschappen - fysische chemie - oppervlaktechemie - surface interactions - colloidal properties - physical chemistry - surface chemistry
Rede Wageningen, 2 februari 1931