The Variety of Odors Produced in Maillard Model Systems and How They Are Influenced by Reaction Conditions

This study is focused on the reactions of isothiocyanates (ITCs) in the presence of amino compounds leading to coloured structures <I>via</I> substituted 2-thiohydantoins. A series of complementary experiments has been done and appropriate reaction conditions and structural prerequisites have been defined. Low-molecular colourants isolated and characterised from the model systems can be sorted into three groups. Yellow to red diastereomeric dehydrodimers of 2-thiohydantoin derivatives that contain an acidic methylene group are formed in mixtures consisted of ITCs and amino acids with α-methylene group in mild acidic to mild alkaline systems. The condensation products of the 2-thiohydantoins with reactive aromatic or heterocyclic carbaldehydes from the Maillard reaction, essential oils etc. comprise a heterogeneous group of mostly yellow colourants. Blue compounds of two types are structurally more complicated structures that arise from <I>N</I>-substituted amino acids and ITCs in alkaline media.

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Acrylamide Formation from Asparagine under Low-Moisture Maillard Reaction Conditions. 1. Physical and Chemical Aspects in Crystalline Model Systems

Journal of Agricultural and Food Chemistry ◽

10.1021/jf0492464 ◽

2004 ◽

Vol 52 (22) ◽

pp. 6837-6842 ◽

Cited By ~ 48

Author(s):

Fabien Robert ◽

Gilles Vuataz ◽

Philippe Pollien ◽

Françoise Saucy ◽

Maria-Isabelle Alonso ◽

...

Keyword(s):

Maillard Reaction ◽

Model Systems ◽

Reaction Conditions ◽

Acrylamide Formation ◽

Physical And Chemical

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Multistage Chemical Recycling of Polyurethanes and Dicarbamates: A Glycolysis–Hydrolysis Demonstration

Sustainability ◽

10.3390/su13063583 ◽

2021 ◽

Vol 13 (6) ◽

pp. 3583

Author(s):

Pegah Zahedifar ◽

Lukasz Pazdur ◽

Christophe M.L. Vande Velde ◽

Pieter Billen

Keyword(s):

Bottom Layer ◽

High Potential ◽

Model Systems ◽

Production Yield ◽

Chemical Recycling ◽

Reaction Conditions ◽

Material Cycle ◽

Hydrolysis Of

The use of polyurethanes and, therefore, the quantity of its scrap are increasing. Considering the thermoset characteristic of most polyurethanes, the most circular recycling method is by means of chemical depolymerization, for which glycolysis is finding its way into the industry. The main goal of polyurethane glycolysis is to recover the polyols used, but only limited attempts were made toward recovering the aromatic dicarbamate residues and derivates from the used isocyanates. By the split-phase glycolysis method, the recovered polyols form a top-layer phase and the bottom layer contain transreacted carbamates, excess glycol, amines, urea, and other side products. The hydrolysis of carbamates results in amines and CO2 as the main products. Consequently, the carbamates in the bottom layer of polyurethane split-phase glycolysis can also be hydrolyzed in a separate process, generating amines, which can serve as feedstock for isocyanate production to complete the polyurethane material cycle. In this paper, the full recycling of polyurethanes is reviewed and experimentally studied. As a matter of demonstration, combined glycolysis and hydrolysis led to an amine production yield of about 30% for model systems. With this result, we show the high potential for further research by future optimization of reaction conditions and catalysis.

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Die unterschiedliche Reaktivität von 1,4-Disilabutan und n-Tetrasilan gegenüber sekundären Aminen / Differences in Reactivity of 1,4-Disilabutane and n-Tetrasilane towards Secondary Amines

Zeitschrift für Naturforschung B ◽

10.1515/znb-1990-1214 ◽

1990 ◽

Vol 45 (12) ◽

pp. 1679-1683 ◽

Cited By ~ 8

Author(s):

Hubert Schmidbaur ◽

Heinz Schuh

Keyword(s):

Silicon Nitride ◽

Model Systems ◽

Secondary Amines ◽

Cleavage Reaction ◽

Reaction Conditions ◽

Two Phase ◽

Leaving Group

1,4-Disilabutane H3SiCH2CH2SiH3 (1) and n-tetrasilane H3SiSiH,SiH2SiH3 were employed as model systems for the preparation of silicon-rich aminosilanes potentially useful for the deposition of silicon nitride Si3N4. 1 reacts with the appropriate equivalents of diethylamine in an alkane solvent and in the presence of the two-phase catalyst NaNH2/18-crown-6 to give the products (Et,N)2SiHCH2CH2SiH3, (Et2N)2SiHCH2CH2SiH2(NEt2), and (Et2N)2SiHCH2CH2SiH(NEt2)2. By contrast, n-Si4H10 undergoes a cleavage reaction under similar conditions to yield H3SiNEt2 and H2Si(NEt2)2 together with a mixture of polysilanes SinH2n+2, the composition of which is depending on the reaction conditions and the nature of the catalyst (NaH and NaNH2). Diethylaminopolysilanes are also formed, but only in trace quantities. Treatment of n-Si4H10 with pyrrole (C4H5N) leads to the formation of trisilane accompanied by the pyrrolylsilanes H2Si(C4H4N)2, HSi(C4H4N)3, and Si(C4H4N)4. The differences in reactivity suggest excellent leaving group properties of silyl anions in the reaction with amines.

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Acrylamide Formation from Asparagine under Low Moisture Maillard Reaction Conditions. 2. Crystalline vs Amorphous Model Systems

Journal of Agricultural and Food Chemistry ◽

10.1021/jf050079x ◽

2005 ◽

Vol 53 (11) ◽

pp. 4628-4632 ◽

Cited By ~ 22

Author(s):

Fabien Robert ◽

Gilles Vuataz ◽

Philippe Pollien ◽

Françoise Saucy ◽

Maria-Isabelle Alonso ◽

...

Keyword(s):

Maillard Reaction ◽

Model Systems ◽

Reaction Conditions ◽

Acrylamide Formation

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Mechanism of Emulsion Polymerization

Rubber Chemistry and Technology ◽

10.5254/1.3547244 ◽

1970 ◽

Vol 43 (1) ◽

pp. 74-94 ◽

Cited By ~ 19

Author(s):

J. L. Gardon

Keyword(s):

Particle Size ◽

Emulsion Polymerization ◽

Correct Choice ◽

Present Form ◽

Model Systems ◽

Reaction Conditions ◽

Consistent Model ◽

Good Accord ◽

Conversion Time ◽

Sophisticated Technology

Abstract Emulsion polymerization is one of the most important processes for the manufacture of polymers for rubbers, plastics, coatings, finishes, and adhesives. By the correct choice of comonomers, initiators, surfactants, and reaction conditions, a great variety of latex products are manufactured which meet many specific requirements in their applications. However, there is a great gap between this mostly empirically developed and sophisticated technology and our scientific understanding of it. The present paper presents a theory based on a single internally consistent model which predicts several experimentally available data of emulsion polymerization: the particle size, the conversion—time relationship, the dependence of particle size and molecular weight on conversion, and the influence of surfactant, of initiator and of monomer. This theory is based on extension of the assumptions first proposed by Smith and Ewart and Haward, and later modified by Stockmayer and O'Toole. It differs from these earlier theories in that the derived relationships are quantitative and contain no adjustable parameters. Also, the validity limits of the predictions are defined. The present form of the theory does not apply to all monomers, initiators, surfactants and reaction conditions commonly used in the practice of emulsion polymerization although its predictions are in good accord with experimental results obtained with model systems complying with the assumed conditions.

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Undecagold labeling of tRNA

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100084521 ◽

1991 ◽

Vol 49 ◽

pp. 44-45

Author(s):

James F. Hainfeld ◽

Kyra M. Alford ◽

Mathias Sprinzl ◽

Valsan Mandiyan ◽

Santa J. Tumminia ◽

...

Keyword(s):

High Resolution ◽

Transmission Electron Micrograph ◽

Anticodon Loop ◽

Electron Micrograph ◽

Reaction Conditions ◽

Scanning Transmission Electron ◽

Transmission Electron ◽

Scanning Transmission

The undecagold (Au11) cluster was used to covalently label tRNA molecules at two specific ribonucleotides, one at position 75, and one at position 32 near the anticodon loop. Two different Au11 derivatives were used, one with a monomaleimide and one with a monoiodacetamide to effect efficient reactions.The first tRNA labeled was yeast tRNAphe which had a 2-thiocytidine (s2C) enzymatically introduced at position 75. This was found to react with the iodoacetamide-Aun derivative (Fig. 1) but not the maleimide-Aun (Fig. 2). Reaction conditions were 37° for 16 hours. Addition of dimethylformamide (DMF) up to 70% made no improvement in the labeling yield. A high resolution scanning transmission electron micrograph (STEM) taken using the darkfield elastically scattered electrons is shown in Fig. 3.

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Nuclear coiled bodies and the nucleolus

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100167834 ◽

1994 ◽

Vol 52 ◽

pp. 20-21

Author(s):

K. Brasch ◽

J. Williams ◽

D. Gallo ◽

T. Lee ◽

R. L. Ochs

Keyword(s):

Mouse Liver ◽

Nuclear Body ◽

Nuclear Bodies ◽

Model Systems ◽

Coiled Body ◽

Rrna Processing ◽

Malignant Cells ◽

Sm Proteins ◽

Coiled Bodies ◽

Unique Protein

Though first described in 1903 by Ramon-y-Cajal as silver-staining “accessory bodies” to nucleoli, nuclear bodies were subsequently rediscovered by electron microscopy about 30 years ago. Nuclear bodies are ubiquitous, but seem most abundant in hyperactive and malignant cells. The best studied type of nuclear body is the coiled body (CB), so termed due to characteristic morphology and content of a unique protein, p80-coilin (Fig.1). While no specific functions have as yet been assigned to CBs, they contain spliceosome snRNAs and proteins, and also the nucleolar protein fibrillarin. In addition, there is mounting evidence that CBs arise from or are generated near the nucleolus and then migrate into the nucleoplasm. This suggests that as yet undefined links may exist, between nucleolar pre-rRNA processing events and the spliceosome-associated Sm proteins in CBs.We are examining CB and nucleolar changes in three diverse model systems: (1) estrogen stimulated chick liver, (2) normal and neoplastic cells, and (3) polyploid mouse liver.

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Microtubule Dynamics and Organelle Transport in Reticulomyxa

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100158510 ◽

1990 ◽

Vol 48 (3) ◽

pp. 194-195

Author(s):

Yih-Tai Chen ◽

Ursula Euteneuer ◽

Ken B. Johnson ◽

Michael P. Koonce ◽

Manfred Schliwa

Keyword(s):

Plasma Membrane ◽

Light Microscopy ◽

Cytoplasmic Dynein ◽

Living Cells ◽

Microtubule Dynamics ◽

Model Systems ◽

Organelle Transport ◽

Biochemical Characteristics ◽

Dependent Transport

The application of video techniques to light microscopy and the development of motility assays in reactivated or reconstituted model systems rapidly advanced our understanding of the mechanism of organelle transport and microtubule dynamics in living cells. Two microtubule-based motors have been identified that are good candidates for motors that drive organelle transport: kinesin, a plus end-directed motor, and cytoplasmic dynein, which is minus end-directed. However, the evidence that they do in fact function as organelle motors is still indirect.We are studying microtubule-dependent transport and dynamics in the giant amoeba, Reticulomyxa. This cell extends filamentous strands backed by an extensive array of microtubules along which organelles move bidirectionally at up to 20 μm/sec (Fig. 1). Following removal of the plasma membrane with a mild detergent, organelle transport can be reactivated by the addition of ATP (1). The physiological, pharmacological and biochemical characteristics show the motor to be a cytoplasmic form of dynein (2).

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