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The article provides "recipes" for teachers to make chemistry laboratory activities for students "minds-on" and forces students to think.

The article provides "recipes" for teachers to make chemistry laboratory activities for students "minds-on" and forces students to think.

The article presents a Predict Explain Observe Explain demonstration to confront and remediate typical student misconceptions about pH and [H+] in strong and weak acids.

Umami (“hartigheid”) is één van de vijf basissmaken en is in het begin van de vorige eeuw ontdekt in zeewier. Umami wordt veroorzaakt door bepaalde vormen van aminozuren, en daar wilden we het fijne van weten. In dit project hebben we eiwitten en de aminozuren waaruit die zijn opgebouwd chemisch gekarakteriseerd en sensorisch beoordeeld. Op termijn is het perspectief om uit zeewier, eendenkroos en reststromen van gewassen eiwitcomponenten te isoleren met toegevoegde waarde qua smaak.

The article provides "recipes" for teachers to make chemistry laboratory activities for students "minds-on" and forces students to think.

Umami (“hartigheid”) is één van de vijf basissmaken en is in het begin van de vorige eeuw ontdekt in zeewier. Umami wordt veroorzaakt door bepaalde vormen van aminozuren, en daar wilden we het fijne van weten. In dit project hebben we eiwitten en de aminozuren waaruit die zijn opgebouwd chemisch gekarakteriseerd en sensorisch beoordeeld. Op termijn is het perspectief om uit zeewier, eendenkroos en reststromen van gewassen eiwitcomponenten te isoleren met toegevoegde waarde qua smaak.

De auteur beschrijft een aantal artikelen uit het Journal of Chemical Education 2016 die interessant en geschikt zijn voor gebruik in het scheikunde onderwijs. De beschreven artikelen bevatten de volgende onderwerpen: fraude in het lab, huishoudbatterij, gravimetrisch titreren, reuzeatomen, duikbootchemie.

De auteur beschrijft een aantal artikelen uit het Journal of Chemical Education 2016 die interessant en geschikt zijn voor gebruik in het scheikunde onderwijs. De beschreven artikelen bevatten de volgende onderwerpen: fraude in het lab, huishoudbatterij, gravimetrisch titreren, reuzeatomen, duikbootchemie.

Over the last 10 years a large set of global environmental assessment studies has been published that include scenario projections. Comparison of these studies shows that there is actually a limited set of scenario families that form the basis of many scenarios used in different environmental assessments. Mapping these scenario families allow a simpler comparison across the different assessments. The fact that many assessments can be positioned within these families gives some confidence of their relevance. It is also noticeable that several recent assessments have been focusing on more focussed policy-scenarios as variant to a single baseline. This is partly a response to a different stage in the policy-making process. While there are clear advantages of both categories of scenarios (explorative scenarios and baseline/policy variants), it might be important to test the robustness of scenario outcomes of the policy-scenario approach against the different storyline scenario-families identified in this paper.

The residential sector plays an important role in the energy system of developing countries. In this paper we introduce a bottom up simulation model for household energy use. The model describes energy demand for several end-use functions based on a set of physical drivers, such as floor space and heating degree days. The model also recognizes different population groups: i.e. urban and rural households, each distinguishing five income quintiles. The model is applied to analyze possible future developments of residential energy use in five developing world regions: India, China, South East Asia, South Africa and Brazil. We find that in each of these regions cooking is currently the main end-use function, but that other functions, such as space heating, cooling and appliances become more important. At the same time, energy consumption slowly shifts towards modern fuels. The model also shows that climate policy can reduce residential energy emissions, but could also slow down the energy transition away from traditional fuels in low income classes. (C) 2011 Elsevier Ltd. All rights reserved.

This study assesses the environmental impact of polyethylene terephthalate (PET) bottle-to-fibre recycling using the methodology of life-cycle assessment (LCA). Four recycling cases, including mechanical recycling, semi-mechanical recycling, back-to-oligomer recycling and back-to-monomer recycling were analysed. Three allocation methods are applied for open-loop recycling, i.e. the “cut-off” approach, the “waste valuation” approach and the “system expansion” approach. Nine environmental impact indicators were analysed, i.e. non-renewable energy use (NREU), global warming potential (GWP), abiotic depletion, acidification, eutrophication, human toxicity, fresh water aquatic ecotoxicity, terrestrial ecotoxicity and photochemical oxidant formation. The LCA results are compared with virgin PET fibre and other commodity fibre products, i.e. cotton, viscose, PP (polypropylene) and PLA (polylactic acid). The LCA results show that recycled PET fibres offer important environmental benefits over virgin PET fibre. Depending on the allocation methods applied for open-loop-recycling, NREU savings of 40–85% and GWP savings of 25–75% can be achieved. Recycled PET fibres produced by mechanical recycling cause lower environmental impacts than virgin PET in at least eight out of a total of nine categories. Recycled fibres produced from chemical recycling allow to reduce impacts in six to seven out of a total of nine categories compared to virgin PET fibres. Note that while mechanical recycling has a better environmental profile than chemical recycling, chemically recycled fibres can be applied in a wider range of applications than mechanically recycled fibres.

Authentic samples of auxin-a, auxin-b and auxin-a lactone - discussed in papers from this laboratory in the period 1931-1944 - are found to be identical with cholic acid, thiosemicarbazide and hydroquinone, respectively. Auxin glutaric acid turns out to be phthalic acid, and the 3,5-dinitrobenzoyl ester of auxin-b is ethyl α-cyanophenylpyruvate. Auxins a and b, as unique individuals, are therefore to be considered as non-existent.

We discuss an implementation of molecular dynamics (MD) simulations on a graphic processing unit (GPU) in the NVIDIA CUDA language. We tested our code on a modern GPU, the NVIDIA GeForce 8800 GTX. Results for two MD algorithms suitable for short-ranged and long-ranged interactions, and a congruential shift random number generator are presented. The performance of the GPU's is compared to their main processor counterpart. We achieve speedups of up to 80, 40 and 150 fold, respectively. With newest generation of GPU's one can run standard MD simulations at 10^7 flops/$., 12 pages, 5 figures. Submitted to Mol. Sim

In dit artikel wordt beschreven hoe je met behulp van homeopathie leerlingen kan interesseren en enthousiasmeren voor het onderwerp verdunningen.

In dit artikel wordt beschreven hoe je met behulp van homeopathie leerlingen kan interesseren en enthousiasmeren voor het onderwerp verdunningen.

De auteur beschrijft een aantal artikelen uit het Journal of Chemical Education 2013 die interessant en geschikt zijn voor gebruik in het scheikunde onderwijs: threshold concepts, tatoeages, NMR-spectroscopie, droogijs,en water, kattenbakvulling, Smartphone als meetinstrument en flipping the classroom.

Many proteins can switch from one conformation to another under the influence of an external driving force, such as the binding to a specific substrate. Using a simple lattice model we show that it is feasible to design protein-like lattice proteins that can have two different conformations, depending on whether or not they are bound to a substrate. We give three different examples of such substrate-induced refolding. In addition, we have explored substrate-induced folding of lattice proteins that do not fold when free in solution. We show that such proteins can bind with the same high specificity as prefolded protein, but have a considerably lower binding free energy. In this way proteins can bind to a substrate in a way that is highly specific, yet reversible.

A series of new semi-synthetic metalloprotein hybrids were created via the covalent binding of organometallic species in the active site of lipases, accordingly resulting in the first active site-directed (ASD) homogeneous artificial metalloenzymes. The use of this method promises the generation of a 2nd coordination sphere by the protein scaffold over an incorporated transition metal complex, thereby promoting stereodirecting properties, i.e. catalytic selectivity, and water solubility to the organometallic fragment, and diversifying the hosting enzyme’s activity. A review of the different metalloenzyme hybridization strategies is given in Chapter 1, with comparisons between their corresponding advantages. The ASD method in combination with N-heterocyclic carbene (NHC) ligands is proposed as a versatile strategy due to the good catalytic activity and water-tolerance of a myriad of known metal(NHC) species. In Chapter 2, two covalent ASD Rh(NHC)-lipase hybrids were created. These and other hybrids of the thesis were characterized by ESI-MS and by the resulting catalytic activity. A Rh-cutinase hybrid showed catalytic activity in the hydrogenation of the ketone acetophenone and the olefin methyl 2-acetamidoacrylate with an enhanced chemoselectivity towards the olefin promoted by the protein scaffold compared to unsupported Rh catalyst. A rhodium-CalB hybrid showed pronounced chemoselective behavior due to the deeper location of the lipase’s active pocket. In Chapter 3, Grubbs-Hoveyda II complexes were reacted with cutinase to form the first covalent ASD artificial enzymes for olefin metathesis. Important metal-protein interactions were observed, like hindered hybridization when bulky N-substituents in the NHC ligands were used and protein-metal distance influence over the catalytic activity with successfully formed hybrids. The ring-closing metathesis (RCM) of N,N-diallyl p-toluenesulfonamide and the cross metathesis (CM) of allylbenzene were achieved, the latter representing the first example of formal CM with metalloenzymes. In Chapter 4, the catalytic asymmetric allylic alkylation of allyl aryls was explored with the first covalent artificial metallo-enzyme based on palladium. PPh3 was needed as an additive to achieve catalytic activity. Its role was studied, discarding Pd(NHC)-protein cleavage and showing activation of the Pd center. Inactive in the alkylation of 1,3-diphenyl allyl acetate with malonate due to sterical hindrance, the hybrids were however active in the alkylation of the smaller 1-phenylallyl acetate. In this case, the stereodirecting influence of the protein scaffold drastically inverted the linear/branched ratio of the products in comparison with unsupported Pd catalysts. In Chapter 5, it was pursued to complement the promotion of a second coordination sphere over a Rh(NHC) hydrogenation catalyst by its compartmentalization between two enzyme hosting units, forming the first monometallic ditopic artificial enzyme. Catalytic studies and computational modeling of the hybrid showed that the catalytic center retained its racemic and chemoselective character as if it were not supported, due to large metal-protein tail allowing for flexibility in the protein-metal-protein conformation. In conclusion, the first covalent homogeneous ASD metalloprotein catalysts have been created. This hybridization method shows its effectiveness for the anchoring of a single catalytic fragment in a family of enzymes and the formation of strong protein-metal interactions, generating catalytic chemoselectivity and regioselectivity.

The BALB/c mouse model for human respiratory syncytial virus infection has contributed significantly to our understanding of the relative role for CD4+ and CD8+ T cells to immune protection and pathogenic immune responses. To enable comparison of RSV-specific T cell responses in different mouse strains and allow dissection of immune mechanisms by using transgenic and knockout mice that are mostly available on a C57BL/ 6 background, we characterized the specificity, level and functional capabilities of CD8+ T cells during primary and secondary responses in lung parenchyma, airways and spleens of C57BL/6 mice. During the primary response, epitopes were recognized originating from the matrix, fusion, nucleo- and attachment proteins, whereas the secondary response focused predominantly on the matrix epitope. C57BL/6 mice are less permissive for hRSV infection than BALB/c mice, yet we found CD8+ T cell responses in the lungs and bronchoalveolar lavage, comparable to the responses described for BALB/c mice. © 2006 Elsevier Inc. All rights reserved. Keywords: Respiratory syncytial virus; C57BL/6; CD8+ T cells; Inactivation; Tetramer

The rate of crystal nucleation of colloids and globular proteins can be enhanced by critical density fluctuations. It has been argued that a closely related phenomenon influences the rate of intramolecular "crystallization" of single-chain polymers. We report Monte Carlo simulations of the free-energy barrier that separates the crystalline state of a homopolymer chain from the disordered state. The simulations show that the barrier for nucleation of the ordered state is drastically lowered as the disordered state changes from a coil to a globule. We discuss the relation of the present findings to intramolecular nucleation of heteropolymers, such as proteins.

We present a model study of a multi-component system that can form low-symmetry ordered phases, even though all pair interactions between the constituent particles are spherically symmetric. Using Monte Carlo simulations and a mean-field model we investigate the thermodynamic, structural, and kinetic aspects of the formation of stripe phases for a simple, multi-component lattice model. This lattice model was chosen to represent a mixture of spherically symmetric DNA-coated colloids with several species of DNA linkers. We predict that the optimal strategy to design a specific low-symmetry phase is the one which not only provides the weakest strength of competitive binding, but also leads to the 'staged' ordering of nanoparticle superstructures.

SummaryHow peroxisomes are formed in eukaryotic cells is unknown but important for insight into a variety of diseases. Both human and yeast cells lacking peroxisomes due to mutations in PEX3 or PEX19 genes regenerate the organelles upon reintroduction of the corresponding wild-type version. To evaluate how and from where new peroxisomes are formed, we followed the trafficking route of newly made YFP-tagged Pex3 and Pex19 proteins by real-time fluorescence microscopy in Saccharomyces cerevisiae. Remarkably, Pex3 (an integral membrane protein) could first be observed in the endoplasmic reticulum (ER), where it concentrates in foci that then bud off in a Pex19-dependent manner and mature into fully functional peroxisomes. Pex19 (a farnesylated, mostly cytosolic protein) enriches first at the Pex3 foci on the ER and then on the maturing peroxisomes. This trafficking route of Pex3-YFP is the same in wild-type cells. These results demonstrate that peroxisomes are generated from domains in the ER.

The efficiency of Markov-Chain Monte Carlo simulations can be enhanced by exploiting information about trial moves that would normally be rejected. The original presentation of this approach was limited to a specific MC sampling scheme. Here we present a general derivation of a method to improve the sampling efficiency of Monte Carlo simulations by collecting information about the microstates that can be linked directly to the sampled point via an independent Markov transition matrix. As an illustration, we show that our approach greatly enhances the efficiency of a scheme to compute the density of states of a square-well fluid.

We report Monte Carlo studies of liquid crystal nucleation in two types of anisotropic colloidal systems: hard rods and hard ellipsoids. In both cases we find that nucleation pathways differ strongly from the pathways in systems of spherical particles. Short hard rods show an effect of self-poisoning. This part of the article is based on a previous publication [T. Schilling, D. Frenkel, Self-poisoning of crystal nuclei in hard-rod liquids, Phys. Rev. Lett. 92 (2004) 085505]. When a crystallite forms, its surfaces are covered preferentially by rods which align perpendicular to the surface. Therefore subsequent growth is stunted. Hard, almost spherical ellipsoids can be compressed to very high densities without crystallization—in contrast to hard spheres, which crystallize easily. When forced to crystallize, ellipsoids form very loosely aggregated nuclei. In both cases nucleation pathways are complex and it is therefore difficult to define an appropriate reaction coordinate. The common strategies of investigation of nucleation problems (i.e. definition of a coordinate and then sampling barrier crossing with well-known techniques) fail in these systems.

The exponential increase in the speed of computers during the past few decades has made it possible to perform simulations that were utterly unfeasible one generation ago. But in many cases, the development of more efficient algorithms has been at least as important. One of the most widely used schemes to simulate manybody systems is the Markov-chain Monte Carlo method (MCMC) that was introduced in 1953 by Metropolis et al. In this algorithm the average properties of a system are estimated by performing a random walk in the configurational space, where each state is sampled with a frequency proportional to its Boltzmann weight. In the Metropolis algorithm, this is achieved by attempting random moves from the current state of the system to a new state. Depending on the ratio of the Boltzmann weights of the new and old states, these trial moves may be either accepted or rejected. Metropolis et al.

The development of models for electrolytes is challenging due to the long-range nature of electric interactions. We propose a novel implementation of a lattice Boltzmann model that solves a number of limitations and inconsistencies in previously proposed variants and discuss the range of parameters the model can cover. We show how the relevant electrohydrodynamic couplings are recovered analyzing a particular electrokinetic phenomena.

The evolutionary reason for the increase in gene length from archaea to prokaryotes to eukaryotes observed in large scale genome sequencing efforts has been unclear. We propose here that the increasing complexity of protein-protein interactions has driven the selection of longer proteins, as longer proteins are more able to distinguish among a larger number of distinct interactions due to their greater average surface area. Annotated protein sequences available from the SWISS-PROT database were analyzed for thirteen eukaryotes, eight bacteria, and two archaea species. The number of subcellular locations to which each protein is associated is used as a measure of the number of interactions to which a protein participates. Two databases of yeast protein-protein interactions were used as another measure of the number of interactions to which each \emph{S. cerevisiae} protein participates. Protein length is shown to correlate with both number of subcellular locations to which a protein is associated and number of interactions as measured by yeast two-hybrid experiments. Protein length is also shown to correlate with the probability that the protein is encoded by an essential gene. Interestingly, average protein length and number of subcellular locations are not significantly different between all human proteins and protein targets of known, marketed drugs. Increased protein length appears to be a significant mechanism by which the increasing complexity of protein-protein interaction networks is accommodated within the natural evolution of species. Consideration of protein length may be a valuable tool in drug design, one that predicts different strategies for inhibiting interactions in aberrant and normal pathways., 13 pages, 5 figures, 2 tables, to appear in Physica A

The endoplasmic reticulum (ER) is a highly versatile protein factory that is equipped with chaperones and folding enzymes essential for protein folding. ER quality control guided by these chaperones is essential for life. Whereas correctly folded proteins are exported from the ER, misfolded proteins are retained and selectively degraded. At least two main chaperone classes, BiP and calnexin/calreticulin, are active in ER quality control. Folding factors usually are found in complexes. Recent work emphasises more than ever that chaperones act in concert with co-factors and with each other.

A planar converter containing quantum dots as wavelength-shifting moieties on top of a solar cell was studied. The highly efficient quantum dots are to shift the wavelengths where the spectral response of the solar cell is low to wavelengths where the spectral response is high in order to improve the conversion efficiency of the solar cell. It was calculated that quantum dots with an emission at 603 nm increase the multicrystalline solar cell short-circuit current by nearly 10%. Simulation results for planar converters on hydrogenated amorphous silicon solar cells show no beneficial effects, due to the high spectral response at low wavelength.

▪ Abstract This review discusses the recent progress that has been made in the application of computer simulations to study crystal nucleation in colloidal systems. We discuss the concept and the numerical methods that allow for a quantitative prediction of crystal-nucleation rates. The computed nucleation rates are predicted from first principles and can be directly compared with experiments. These techniques have been applied to study crystal nucleation in hard-sphere colloids, polydisperse hard-sphere colloids, weakly charged or slightly soft colloids, and hard-sphere colloids that are confined between two-plane hard walls.

The Markov chain Monte Carlo method is an important tool to estimate the average properties of systems with a very large number of accessible states. This technique is used extensively in fields ranging from physics to genetics and economics. The rejection of trial configurations is a central ingredient in existing Markov chain Monte Carlo simulations. I argue that the efficiency of Monte Carlo simulations can be enhanced, sometimes dramatically, by properly sampling configurations that are normally rejected. This “waste-recycling” of microstates is useful in sampling schemes in which only one of a large set of trial configurations is accepted. It differs fundamentally from schemes that extract information about the density of macrostates from virtual Monte Carlo moves. As a simple illustration, I show that the method greatly improves the calculation of the order-parameter distribution of a two-dimensional Ising model. This method should enhance the efficiency of parallel Monte Carlo simulations significantly.

We propose that the first stage of membrane fusion need not be the formation of a single stalk. Instead, we consider a scenario for defect-induced membrane fusion that proceeds cooperatively via multiple stalk formation. The defects (stalks or pores) attract each other via membrane-mediated capillary interactions that result in a condensation transition of the defects. The resulting dense phase of stalks corresponds to the so-called fusion intermediate. PACS: 87.16.Dg Membranes, bilayers, and vesicles - 68.05.-n Liquid-liquid interfaces - 64.60.-i General studies of phase transitions

We describe an approach to use multiple-histogram methods in combination with static, biased Monte Carlo simulations. To illustrate this, we computed the force-extension curve of an athermal polymer from multiple histograms constructed in a series of static Rosenbluth Monte Carlo simulations. From the complete histogram of the distribution function of the end-to-end vectors of the polymer chain, we can efficiently compute the polymer force-extension curve.

Human immunodeficiency virus binds and enters cells via the Envelope glycoprotein gp160 at its surface. In infected cells, gp160 is found not only on the plasma membrane but also in the endoplasmic reticulum (ER). Our aim was to establish rate-determining steps in the maturation process of gp160, using a radioactive pulse-chase approach. We found that gp160 has an intricate folding process: disulfide bonds start to form during synthesis but undergo extensive isomerization until the correct native conformation is reached. Removal of the leader peptide critically depends on formation of at least some disulfide bonds in subunit gp120 during folding. Envelope folds extremely slowly and therefore resides in the ER longer than other proteins, but the yield of properly folded molecules is high and degradation is undetectable. The large quantity of gp160 in the ER hence is a result of its slow transit through this compartment. We show here that newly synthesized HIV-1 Envelope glycoprotein apparently follows a slow but high-yield folding path in which co- and post-translational formation of disulfide bonds in gp120, disulfide isomerization and conformation dependent removal of the leader sequence are determining and intertwined events.

We present a systematic numerical study of the phase behavior of square-well fluids with a "patchy" short-ranged attraction. In particular, we study the effect of the size and number of attractive patches on the fluid–fluid coexistence. The model that we use is a generalization of the hard sphere square well model. The systems that we study have a stronger tendency to form gels than the isotropic square-well system. For this reason, we had to combine Gibbs ensemble simulations of the fluid–fluid coexistence with a parallel tempering scheme. For moderate directionality, changes of the critical density and the width of coexistence curves are small. For strong directionality, however, we find clear deviations from the extended law of corresponding states: in contrast to isotropic attractions, the critical point is not characterized by a universal value of the reduced second virial coefficient. Furthermore, as the directionality increases, multiparticle bonding affects the critical temperature. We discuss implications for the phase behavior, and possibly crystallization, of globular proteins.

Using thermodynamic integration, we calculate free energies of the melt and the crystalline phases of a model system of C198H398 with a realistic all-atom potential. We use the Gibbs–Duhem integration scheme to calculate the melting curve over the experimentally relevant pressure range. The crystal structure and the melting curve obtained from our simulation are in good quantitative agreement with the available experimental results.

The novel trinuclear complexes [(Pt{C6H3(CH2NMe22,6)2})2(μ-Hbiim)2Os(O=PPh3)2](NO3)(SO3CF3)2 [C6H3(CH2NMe2-2,6)2 = pincer ligand, H2biim = 2,2′-biimidazole] and [(PdL)2(μ-biim)2Os(O=PPh3)2](NO3)3 (L = cod, 1,5-cyclooctadiene or L = en, ethylene-1,2-diamine) were prepared by the reaction of the mononuclear complex [Os(H2biim)2(O=PPh3)2](NO3)3 with [Pt{C6H3(CH2NMe2-2,6)2}](SO3CF3), or with PdL(NO3)2 (L = cod or L = en), in the presence of a base. The exchange reaction between [Os(Hbiim)2(O=PPh3)2](NO3)3 and [Me2NH2][RhCl4(NHMe2)] led to the formation of [Os(Hbiim)2(O=PPh3)2][RhCl4(NHMe2)]. The solid-state structures of [Os(Hbiim)2(O=PPh3)2][RhCl4(NHMe2)] and [(Pt{C6H3(CH2NMe2-2,6)2})2(μ-Hbiim)2Os(O=PPh3)2](NO3)(SO3CF3)2·4H2O were determined by single-crystal X-ray diffraction. The crystals of [Os(Hbiim)2(O=PPh3)2][RhCl4(NHMe2)] are triclinic with a space group P , with a = 10.4293(5), b = 10.6365(6), c = 13.0287(7) A, β = 91.6840(10), γ = 109.8540(10)°, V = 1316.14(12) A3, Z = 1. The crystals of the complex [(Pt{C6H3(CH2NMe2-2,6)2})2(μHbiim)2Os(O=PPh3)2](NO3)(SO3CF3)2·4H2O are triclinic with a space group P , with a = 12.604(3), b = 13.471(3), c = 14.347(3) A, β =77.530(5), γ = 66.613(4)°, V = 2005.6(7) A3, Z = 1. Deprotonation of 2,2′-biimidazole in the mononuclear osmium complex, followed by coordination to an additional transition metal fragment leads to a modification of the ligand field and a variation of the redox properties of the OsIII center. [{Pd(cod)}2(μ-biim)2Os(O=PPh3)2](NO3)3 shows significant catalytic activity towards hydrogenation of terminal and cyclic alkenes. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

We report a numerical study of crystallization and melting in bulk statistical homogeneous (random), homogeneous (slightly alternating), and heterogeneous (produced in a batch reaction) copolymers formed by crystallizable monomers and noncrystallizable comonomers. In our dynamic Monte Carlo simulations of lattice chains, the current model further assumes that the comonomers cannot move into crystalline regions by sliding diffusion of the chains. We find that both the overall composition and the statistical distribution of the monomers affect the phase-transition temperature, the resulting relative crystallinity, and the crystal morphology. However, the final absolute crystallinity of homogeneous copolymers seems insensitive to these parameters. Intramolecular segregation between monomers and comonomers is accompanied by crystallization, demonstrating the concept of sequence segregation or nanophase separation of statistical copolymers with assembling structures like in thermoplastic elastomers. Moreover, if crystallization of homogeneous copolymers has started but not yet completed on cooling, subsequent heating will show cold crystallization before melting, which can be attributed to insertion-mode lamellar growth. For heterogeneous copolymers, intermolecular segregation occurs on cooling before crystallization. On the basis of our observations, a pair of master melting and crystallization curves for the crystallinity of a statistical copolymer as a function of temperature are suggested to reflect the characteristic of the monomer-sequence-length distribution. This suggestion facilitates the clarification to the kinetic disturbance in local temperature regions and to the principle of some fractionation methods, such as temperature rising elution fractionation (TREF).

Using free-energy calculations on small crystalline clusters, we estimate the free-energy density γSL for the solid–liquid equimolar interface of a system of hard-sphere colloids. By studying the behavior of a crystallite at coexistence, we determine the dependence of γSL on the radius of curvature of the interface. An extrapolation to infinite radius of curvature (flat interface), yields γSL(R → ∞) = 0.616(3), in good agreement with recent numerical estimates. Subsequently, we consider the dependence of the interfacial free-energy density on the degree of supersaturation. Our simulations suggest that the γSL associated with the equimolar surface is fairly insensitive to changes in supersaturation.

We present a numerical simulation of the phase behavior of a simple model for a protein solution. We find that this system can occur in three phases, namely a dilute liquid, a dense liquid and a crystal. The transition from dilute-liquid to dense-liquid takes place in the regime where the fluid phase is metastable with respect to the crystal. We have computed the relative stabilities of different crystal morphologies. In addition, we have analyzed the "nucleation" of the native state of an isolated lattice protein. Using a "Gõ" model [N.Gõ, J. Stat. Phys. 30, 413 (1983)] to describe the protein, we show that a first order transition exists between the native and the coil state. We show this by analyzing the free energy barrier for the coil-to-native transition.

The chemoenzymic synthesis is described of β-D-Galp-(1→4)-β-D-Glcp-(1→6)-[(β-D-Galp)-(1→4)]-β-D-GlcpNAc-(1→3)-β-D-Galp-(1→O(CH2)6NH2) 20 and β-D-Galp-(1→4)-β-D-Glcp-(1→6)-[(β-D-Galp)-(1→4)]-β-D-GlcpNAc-(1→3)-β-D-Galp-(1→4)-β-D-Glcp-(1→O(CH2)6NH2) 21, representing penta- and hexasaccharide fragments of the Streptococcus pneumoniae type 14 capsular polysaccharide. In a chemical approach the intermediate tetra- and pentasaccharide fragments 18 and 19, respectively, were synthesised, wherein the non-terminal N-acetyl-β-D-glucosamine residues were not yet galactosylated. Both intermediates were found to be good acceptor substrates for bovine milk β-1,4-galactosyltransferase. The title oligosaccharides form suitable compounds for conjugation with carrier proteins, to be tested as potential vaccines in animal models.

The bulk thermodynamic properties of proteins originate from a varied and complex combination of interactions. We propose a simple model for the formation of ordered two-dimensional aggregates based on the interactions between pairs of annexin V molecules. Simulations of this model are shown to reproduce the experimental observations of a honeycomb (p6) and a triangular (p3) crystalline phase. The simulations indicate that the transition between these two phases is first order. While this model is extremely simple in that it relies only on hard body and short-range directional interactions, it nevertheless captures the essential physics of the interactions between the protein molecules and reproduces the phase behavior observed in electron microscopy and atomic force microscopy experiments.

These lectures illustrate some of the concepts of soft-condensed matter physics, taking examples from colloid physics. Many of the theoretical concepts will be illustrated with the results of computer simulations. After a brief introduction describing interactions between colloids, the paper focuses on colloidal phase behavior (in particular, entropic phase transitions), colloidal hydrodynamics and colloidal nucleation.

The bulk thermodynamic properties of membrane proteins originate from a complex combination of molecular interactions. We propose a simple model based on the pair interactions between a model membrane protein, annexin V. The experimental observations of a honeycomb (p6) and a triangular (p3) phase are successfully reproduced with Monte Carlo computer simulations. Grand canonical simulations and a newly developed "strip"-move constant pressure technique reveal the stability of a dilute fluid phase and a dense solid phase, not observed with the current experimental technology. While this model is extremely simple in that it relies only on hard-body and short-range directional interactions, it nevertheless captures the essential physics of the interactions between the protein molecules and reproduces the phase behavior observed in experiments.

Treatment of the diaminobenzene [C{6}H{4}{CH{2}NMe{2}}{2}-1, 3] (NCN-H, 1) with one or two equivalents of cis-PtCl{2}(DMSO){2} leads to exclusive formation of the doubly cycloplatinated species [C{6}H{4}{CH{2}NMe{2}}{2}-1,5-{PtCl(DMSO)}{2}-2,4] (3), which upon addition of triphenylphosphine yields the bisphosphine adduct [C{6}H{4}{CH{2}NMe{2}}{2}-1,5-{PtCl(PPh{3})}{2}-2,4] (4). The X-ray molecular structure of 4 revealed the presence of highly distorted square planar Pt(II) centers which is caused by close proximity of the two phosphine donor ligands. Complexes of type 3 can be regarded as suitable starting materials for the directional build-up of larger macromolecular structures.

OmpT from Escherichia coli belongs to a family of highly homologous outer membrane proteases, known as omptins, which are implicated in the virulence of several pathogenic Gram-negative bacteria. Here we present the crystal structure of OmpT, which shows a 10-stranded antiparallel beta-barrel that protrudes far from the lipid bilayer into the extracellular space. We identified a putative binding site for lipopolysaccharide, a molecule that is essential for OmpT activity. The proteolytic site is located in a groove at the extracellular top of the vase-shaped beta-barrel. Based on the constellation of active site residues, we propose a novel proteolytic mechanism, involving a His-Asp dyad and an Asp-Asp couple that activate a putative nucleophilic water molecule. The active site is fully conserved within the omptin family. Therefore, the structure described here provides a sound basis for the design of drugs against omptin-mediated bacterial pathogenesis. Coordinates are in the Protein Data Bank (accession No. 1I78)