Chemistry

Coupled reactions

Coupled reactions


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Are you struggling to understand the Linked Reactions unit? Then you may be missing the following basics:

RG laws and experimental findings30 min.

ChemistryPhysical chemistrykinetics

In the learning unit, basic knowledge of the kinetics of chemical reactions as well as reaction orders and partial orders are presented.

Integrated RG laws of simple reactions15 minutes.

ChemistryPhysical chemistrykinetics

This learning unit shows the reaction rate laws in the form of the product approach in the form of a table for the most important reaction types.

Reversible reactions and equilibrium45 min.

ChemistryPhysical chemistrykinetics

In this learning unit we look at reactions in which the products react again to the educts. One speaks here of reversible reactions. The reaction process is thus determined by the simultaneous course of two reactions.


Both in theory and in practice (e.g. enzymatic processes in the body) there are many examples of reactions in which a certain substance A is converted into a substance B and this in turn immediately reacts to a third substance C.

The partial reactions are coupled with each other - if there are equilibrium reactions, the law of mass action (MWG) can be applied to each partial reaction. If you also solve both expressions for [B] and equate them, you get Ktotal.

In the equation above, this represents Ktotal represents the product of the equilibrium constants of the partial reactions. This allows the partial reactions coupled to one another to be brought together to form an overall reaction. Substance B then no longer appears in the equation of the law of mass action.

Such a coupling of systems becomes interesting if, for example, partial reaction 1 has a small K1-Value and therefore little B is provided. If, however, partial reaction 2 has a large one K2Value increases, the substance B is largely removed from the equilibrium with the formation of C. Due to the principle of the smallest constraint, the equilibrium of partial reaction 1 is shifted, with B being continuously replenished. Although the K1Value is relatively small, the overall reaction still runs from A to C.


Content and learning objectives

The module BCh 20 1.2 combines theory and practice when introducing the chemistry of the (main group) elements and working in the chemical laboratory. The students should acquire chemical knowledge of the main group elements, important compounds and their reactions (chemical chemistry of the main group elements), which will be taken up and expanded in the practical course. When dealing with analytical detection reactions, in addition to basic experimental skills, a deeper understanding of reactions in aqueous solution should be acquired, especially with regard to coupled reaction equilibria.

The chemistry of substances (of the main group elements) is of course an indefinable area. In every introductory textbook (e.g. Riedel, Housecroft / Sharpe) a different selection is made here. When dealing with chemical chemistry, it is therefore not primarily about memorizing as many facts as possible, but rather about gaining a coherent picture of the properties and possibilities of an element and its connections. This is achieved primarily through individual engagement with the material (especially with the help of textbooks). Self-study is therefore the most important component in learning chemistry. In module BCh 20 1.2 this is supported by a lecture and a course performance (poster presentation).

The practical training in chemistry begins with the practical course "Qualitative Analysis, Part 1" in the second part of the module. The aim of this training is that the Bachelor graduates can accurately carry out, document and evaluate synthetic, analytical and physicochemical experiments. Important skills and knowledge that must be acquired / trained on the way to this goal include:

  • Observational ability
  • care
  • safe performance of basic laboratory operations
  • critical handling of experimental results
  • Comprehensible documentation of the experiments carried out

The analytical tasks in the "Qualitative Analysis" internship have a low level of manual difficulty; all laboratory operations are carried out with simple devices such as test tubes, Pasteur pipettes or Erlenmeyer flasks. In this way, the students can concentrate fully on the precise implementation of the analytical work and the precise observation of the reactions taking place.


Tyrosine phosphatases

Tyrosine phosphatases can also act as transmembrane receptors and play an important role, for example, in the activation of T and B lymphocytes by the CD45 protein or in the deactivation of the JAK / STAT response by SHP 1 and 2. Sometimes they practice theirs Role in the activation of a signaling pathway by the fact that it is through the ligand deactivated and so no longer have an inhibiting effect on the signal path. This can also happen together with the tyrosine kinases, which, when activated, attach more phosphate groups to a certain protein, while the tyrosine phosphatases split off fewer phosphate groups, which leads to an even stronger activation.


Coupled reactions - chemistry and physics

October 15, 2019 / Kiel. More short-term heat waves, long-term warming and acidification, increasing eutrophication and oxygen depletion - marine ecosystems are exposed to a wide range of changes. The reactions of the organisms living in the sea to some of these factors are just as varied. Biologists at the GEOMAR Helmholtz Center for Ocean Research Kiel have now been able to demonstrate for the first time in a large alga that its response to different environmental changes can be positively and negatively coupled - which leads to an acceleration or braking of its adaptation. The study has now been published in the international online journal Scientific Reports.

The stress on marine ecosystems is increasing. The warming of the oceans, the drop in the pH value of the sea water, the supply of nutrients and the loss of oxygen are a problem for them. It is true that individual factors can mean an advantage for certain species. Other changes can also severely restrict the habitat of the same species. The different effects make it very difficult to estimate future shifts in species diversity. "One of the central questions is whether the reactions to various changes are positively or negatively related to each other or whether they run independently of one another," says Prof. Dr. Martin Wahl, marine biologist at the GEOMAR Helmholtz Center for Ocean Research Kiel.

Biologists from GEOMAR and the University of Rostock are now publishing a study in the international online journal Scientific Reports that shows for the first time that a key species in coastal ecosystems, the bladder wrack Fucus vesiculosus, is linked to several changes at the genetic level. “This can both accelerate and block reactions of the bladderwrack to changes,” explains Professor Wahl, lead author of the study.

The bladderwrack Fucus vesiculosus is a brown alga that lives on hard surfaces along the coasts of the North Atlantic and in the North and Baltic Seas. Like other algae, it plays an important role in binding carbon in the sea. It also forms the basis of the ecosystem on the respective coastline. In the Baltic Sea, but also in its other areas of distribution, the stocks of Fucus vesiculosus have declined sharply since the beginning of the 21st century. The exact reasons for this have not yet been finally clarified.

For their study, the researchers used a special test facility, the Kiel Outdoor Benthocosmen (KOB). It consists of a total of twelve test chambers in which coastal ecosystems can be simulated on a small scale. Thanks to complex control technology, several environmental parameters can be manipulated. Since the KOB are located on a pontoon in the Kiel inner fjord and are supplied directly with water from the fjord, the environmental conditions within the test basins come very close to nature.

In the test chambers, the team exposed genetically different families of the bladderwrack to increased carbon dioxide conditions and the resulting lower pH values ​​in the water, warm phases, increased nutrient input and phases with a lack of oxygen over a period of twelve months. “Each of the families was the offspring of just one pair of parents,” explains Professor Wahl.

The reactions to the various changes were clearly linked to one another. Families who can tolerate lower pH values ​​could also tolerate warming and higher nutrient values ​​- and vice versa. At the same time, however, precisely these families were significantly more susceptible to oxygen deprivation. "In nature this could mean that a bladderwrack population that has adapted to overfertilization and summer heat is particularly badly damaged or completely destroyed in autumn by the upwelling of oxygen-free water from the depths," says Martin Wahl.

Overall, the team has not only succeeded in providing the first evidence that reactions to various symptoms of global change can be linked to a marine primary producer. “The study also shows that in the future we will still need research that examines the reactions of organisms to several environmental changes occurring at the same time or at different times. Otherwise it will be difficult to make reliable statements about the future development of ecosystems in the sea, ”emphasizes Professor Wahl.

Scientific contact:

Prof. Dr. Martin Wahl, [email protected]

Original publication:

Al-Janabi, B., M. Wahl, U. Karsten, A. Graiff, and I. Kruse (2019): Sensitivities to global change drivers may correlate positively or negatively in a foundational marine macroalga. Scientific Reports, https://doi.org/10.1038/s41598-019-51099-8

Features of this press release:
Journalists, scientists
Biology, sea / climate
supraregional
research results
German


The importance of G-protein-coupled receptors for medicine

Medicinal substances

In modern medicine, G-protein-coupled receptors occupy a key position: about 60-160% of all prescription drugs currently on the market act on G-protein-coupled receptors. These drugs include the commonly prescribed beta blockers, neuroleptics, antihistamines, opioids and sympathomimetics. New drugs that act via G-protein-coupled receptors, such as the triptans, setrons and sartans, have also achieved great importance in recent years.


Bladderwrack shows coupled reactions to environmental changes

The stress on marine ecosystems is increasing. The warming of the oceans, the drop in the pH value of the sea water, the supply of nutrients and the loss of oxygen are a problem for them. It is true that individual factors can mean an advantage for certain species.

Other changes can also severely restrict the habitat of the same species. The different effects make it very difficult to estimate future shifts in species diversity.

"One of the central questions is whether the reactions to various changes are positively or negatively related to each other or whether they run independently of one another," says Prof. Dr. Martin Wahl, marine biologist at the GEOMAR Helmholtz Center for Ocean Research Kiel.

Biologists from GEOMAR and the University of Rostock are now publishing a study in the international online journal Scientific Reports that shows for the first time that a key species in coastal ecosystems, the bladder wrack Fucus vesiculosus, is linked to several changes at the genetic level.

“This can both accelerate and block reactions of the bladderwrack to changes,” explains Professor Wahl, lead author of the study.

The bladderwrack Fucus vesiculosus is a brown alga that lives on hard surfaces along the coasts of the North Atlantic and in the North and Baltic Seas. Like other algae, it plays an important role in binding carbon in the sea. It also forms the basis of the ecosystem on the respective coastline.

In the Baltic Sea, but also in its other areas of distribution, the stocks of Fucus vesiculosus have declined sharply since the beginning of the 21st century. The exact reasons for this have not yet been finally clarified.

For their study, the researchers used a special test facility, the Kiel Outdoor Benthocosmen (KOB). It consists of a total of twelve test chambers in which coastal ecosystems can be simulated on a small scale.

Thanks to complex control technology, several environmental parameters can be manipulated. Since the KOB are located on a pontoon in the Kiel inner fjord and are supplied directly with water from the fjord, the environmental conditions within the test basins come very close to nature.

In the test chambers, the team exposed genetically different families of the bladderwrack to increased carbon dioxide conditions and the resulting lower pH values ​​in the water, warm phases, increased nutrient input and phases with a lack of oxygen over a period of twelve months. “Each of the families was the offspring of just one pair of parents,” explains Professor Wahl.

The reactions to the various changes were clearly linked to one another. Families who can tolerate lower pH values ​​could also tolerate warming and higher nutrient values ​​- and vice versa. At the same time, however, precisely these families were significantly more susceptible to oxygen deprivation.

"In nature this could mean that a bladderwrack population that has adapted to overfertilization and summer heat is particularly badly damaged or completely destroyed in autumn by the upwelling of oxygen-free water from the depths," says Martin Wahl.

Overall, the team has not only succeeded in providing the first evidence that reactions to various symptoms of global change can be linked to a marine primary producer.

“The study also shows that in the future we will still need research that examines the reactions of organisms to several environmental changes occurring at the same time or at different times. Otherwise it will be difficult to make reliable statements about the future development of ecosystems in the sea, ”emphasizes Professor Wahl.


Coupled pendulums

as coupled pendulum one denotes two or more z. B. interconnected by a spring or a loaded thread Pendulumthat influence each other, i.e. cannot oscillate independently of each other. The simplest form of coupled pendulum is that Double pendulum (Fig.).

If you couple two filament pendulums of the same length and mass (sympathetic pendulum) and if one of the pendulums vibrates by bumping it, there is his Vibrational energy via the coupling gradually to the other pendulum until the entire oscillation energy is in the other pendulum and the first pendulum comes to rest. Then the roles are reversed: the now resting pendulum is excited by the now swinging pendulum and the vibration energy wanders back again.

The oscillation energy "shuttles" back and forth between the two pendulums, whereby both pendulums alternately reach the state of rest or maximum oscillation. This continues until the mechanical energy is consumed by friction processes.

The described oscillation of the sympathetic pendulum is a special case of a beat. If the pendulums are not precisely coordinated with one another, chaotic movements can occur. Beating phenomena do not occur if the two sympathetic pendulums are excited at the same time in such a way that both oscillate either in the same direction or in opposite directions with the same amplitude.


Structure

Due to their structure, G-protein-coupled receptors belong to the superfamily of heptahelical transmembrane proteins (common synonyms: seven transmembrane domain receptors, 7-TM receptors and heptahelical receptors). They consist of subunits with seven (Greek "hepta“) The (transmembrane) helical structures that span the cell membrane and are connected by three intracellular and three extracellular loops. G protein-coupled receptors have an extracellular or transmembrane binding domain for a ligand. The G-protein binds to the inside of the cell (intracellular) side of the receptor.

For a long time, the structure of G-protein-coupled receptors could only be predicted on the basis of the analogy to the known structure of bacteriorhodopsin. The three-dimensional structure elucidation of a G-protein-coupled receptor in vertebrates, the rhodopsin of domestic cattle, was achieved in 2000 with the help of the X-ray structure analysis & # 912 & # 93. The crystallization and structure elucidation of other G protein-coupled receptors, on the other hand, is more difficult because of their physicochemical properties and because of the low density of receptors in the membrane. Therefore, it was not until 2007 that the crystal structure of a ligand-activated G protein-coupled receptor (human β2Adrenoceptor) using technical tricks such as the use of stabilizing antibodies or fusion with easily crystallizable proteins. & # 913 & # 93 & # 914 & # 93

In the meantime, the three-dimensional structure, including that of the transmembrane domains, for numerous G-protein-coupled receptors in humans or animal species has been elucidated with the aid of X-ray crystal analysis using fusion proteins or methods for thermal stabilization. As of 2012, this applies to the β1-Adrenoceptor & # 915 & # 93, the A2A-Adenosine Receptor & # 916 & # 93, the D3-Dopamine receptor & # 917 & # 93, the opioid receptors κ & # 918 & # 93, μ & # 919 & # 93, δ & # 9110 & # 93, nociceptin & # 9111 & # 93, the S1P1- Receptor & # 9112 & # 93, the muscarinic M2 & # 9113 & # 93 and M3-Acetylcholine receptors & # 9114 & # 93, the histamine H1Receptor & # 9115 & # 93, the chemokine receptor CXCR4 & # 9116 & # 93, the neurotensin receptor NTS1 & # 9117 & # 93 and the protease-activated receptor PAR1 & # 9118 & # 93. The three-dimensional structure of the natural human chemokine receptor CXCR1 was determined by means of nuclear magnetic resonance spectroscopy. & # 9119 & # 93 For numerous other G-protein-coupled receptors, at least parts of the structure, such as that of the extracellular domains, could be determined experimentally. In addition, with the rhodopsin of the Japanese flying squid, the structure of a G-protein-coupled receptor in invertebrates is known. & # 9120 & # 93 In 2011, a GPCR in the activated state, i.e. complexed with an agonist & # 9121 & # 93 and G-heterotrimer, was recorded in structural detail for the first time. & # 9122 & # 93

Transmembrane domains

The seven membrane-spanning helical domains of G-protein-coupled receptors, which are arranged counterclockwise when looking at the receptor from the extracellular side, are responsible for anchoring the receptor in the cell membrane. The transmembrane domains III-VI in particular harbor binding sites for a ligand. The transmembrane domains I, II and IV may play a role in the di- and oligomerization of G-protein-coupled receptors.

In contrast to the extracellular and intracellular domains, the transmembrane domains are highly conserved within the family of G protein-coupled receptors. Some amino acid sequences (motifs) within the transmembrane domains are characteristic of many G-protein-coupled receptors. For example, the E / DRY motif of transmembrane domain III and the NPxxY motif of transmembrane domain VII can be found in almost all rhodopsin-like receptors. They are assigned an important role in receptor activation.

Extracellular Domains

Some G-protein coupled receptors, such as & # 160B. the metabotropic glutamate receptors have their primary ligand binding site in their extracellular N-terminal domain. These receptors are characterized by long N-terminal amino acid sequences (up to 2800 amino acids), while receptors with intracellular ligand binding domains usually only have short residues (mostly below 30 amino acids). The N-terminus and extracellular domains of the receptor are often glycosylated.

Large structural differences could also be found in the second extracellular loop (EL 2), which is located near the ligand binding site of the rhodopsin-like G protein-coupled loop. Often either β-hairpin or α-helix motifs can be found in this loop. In the second extracellular loop and at the beginning of the third transmembrane domain of the receptor there are two conserved cysteines capable of forming disulfide bridges, which stabilize the structure of the receptor by binding the transmembrane domains III to V to one another. In contrast to this, the extracellular loop 2 of the κ-opioid receptor, for example, is only stabilized via a disulfide bridge. & # 918 & # 93

Intracellular Domains

The intracellular side of the receptor is equipped with binding sites for G-proteins and other signaling molecules. The amino acids close to the transmembrane domain of the second (IL 2) and third intracellular loops (IL 3) as well as the C-terminal residue adjoining the 7th transmembrane domain are involved in the binding of G proteins. The intracellular C-terminal part is usually very short (usually less than 50 amino acids). Some G-protein-coupled receptors, such as the gonadotropin-releasing hormone receptor, lack this part. An eighth helix (Hx 8) beginning with a conserved cysteine ​​and running parallel to the cell membrane can also be attached directly to the intracellular end of the 7th transmembrane domain. The helix 8 often carries fatty acid residues, such as palmitic acid and oleic acid residues, which serve to anchor this helix in the cell membrane.


Coupled reactions - chemistry and physics

October 15, 2019 / Kiel. More short-term heat waves, long-term warming and acidification, increasing eutrophication and oxygen depletion - marine ecosystems are exposed to a wide range of changes. The reactions of the organisms living in the sea to some of these factors are just as varied. Biologists at the GEOMAR Helmholtz Center for Ocean Research Kiel have now been able to demonstrate for the first time in a large alga that its response to different environmental changes can be positively and negatively coupled - which leads to an acceleration or braking of its adaptation. The study has now been published in the international online journal Scientific Reports.

The stress on marine ecosystems is increasing. The warming of the oceans, the drop in the pH value of the sea water, the supply of nutrients and the loss of oxygen are a problem for them. It is true that individual factors can mean an advantage for certain species. Other changes can also severely restrict the habitat of the same species. The different effects make it very difficult to estimate future shifts in species diversity. "One of the central questions is whether the reactions to various changes are positively or negatively related to each other or whether they run independently of one another," says Prof. Dr. Martin Wahl, marine biologist at the GEOMAR Helmholtz Center for Ocean Research Kiel.

Biologists from GEOMAR and the University of Rostock are now publishing a study in the international online journal Scientific Reports that shows for the first time that a key species in coastal ecosystems, the bladder wrack Fucus vesiculosus, is linked to several changes at the genetic level. “This can both accelerate and block reactions of the bladderwrack to changes,” explains Professor Wahl, lead author of the study.

The bladderwrack Fucus vesiculosus is a brown alga that lives on hard surfaces along the coasts of the North Atlantic and in the North and Baltic Seas. Like other algae, it plays an important role in binding carbon in the sea. It also forms the basis of the ecosystem on the respective coastline. In the Baltic Sea, but also in its other areas of distribution, the stocks of Fucus vesiculosus have declined sharply since the beginning of the 21st century. The exact reasons for this have not yet been finally clarified.

For their study, the researchers used a special test facility, the Kiel Outdoor Benthocosmen (KOB). It consists of a total of twelve test chambers in which coastal ecosystems can be simulated on a small scale. Thanks to complex control technology, several environmental parameters can be manipulated. Since the KOB are located on a pontoon in the Kiel inner fjord and are supplied directly with water from the fjord, the environmental conditions within the test basins come very close to nature.

In the test chambers, the team exposed genetically different families of the bladderwrack to increased carbon dioxide conditions and the resulting lower pH values ​​in the water, warm phases, increased nutrient input and phases with a lack of oxygen over a period of twelve months. "Each of the families was the offspring of just one pair of parents," explains Professor Wahl.

The reactions to the various changes were clearly linked to one another. Families who can tolerate lower pH values ​​could also tolerate warming and higher nutrient values ​​- and vice versa. At the same time, however, precisely these families were significantly more prone to oxygen deprivation. "In nature this could mean that a bladderwrack population that has adapted to overfertilization and summer heat is particularly badly damaged or completely destroyed in autumn by the upwelling of oxygen-free water from the depths," says Martin Wahl.

Overall, the team has not only succeeded in providing the first evidence that reactions to various symptoms of global change can be linked to a marine primary producer. “The study also shows that in the future we will still need research that examines the reactions of organisms to several environmental changes occurring at the same time or at different times. Otherwise it will be difficult to make reliable statements about the future development of ecosystems in the sea, ”emphasizes Professor Wahl.

Scientific contact:

Prof. Dr. Martin Wahl, [email protected]

Original publication:

Al-Janabi, B., M. Wahl, U. Karsten, A. Graiff, and I. Kruse (2019): Sensitivities to global change drivers may correlate positively or negatively in a foundational marine macroalga. Scientific Reports, https://doi.org/10.1038/s41598-019-51099-8

Features of this press release:
Journalists, scientists
Biology, sea / climate
supraregional
research results
German


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