Pyrene-tagged carbohydrate-based mixed P/S ligand: spacer effect on the Rh(i)-catalyzed hydrogenation of methyl α-acetamidocinnamate

2017 ◽  
Vol 15 (27) ◽  
pp. 5772-5780 ◽  
Author(s):  
Juan Francisco Moya ◽  
Christian Rosales ◽  
Inmaculada Fernández ◽  
Noureddine Khiar
Keyword(s):  
Chain Length ◽  
Active Catalyst ◽  
Enantioselective Hydrogenation ◽  
Release Process ◽  
Catch And Release ◽  
Rhodium Atom

The chain length between the pyrene group and the rhodium atom in mixed P/S catalysts is crucial in the enantioselective hydrogenation of enamides, and the most active catalyst can be used in catch and release process.

scholarly journals Dead or alive—estimating post-release mortality of Atlantic cod in the recreational fishery

2013 ◽  
Vol 70 (4) ◽  
pp. 864-872 ◽  
Author(s):  
Marc Simon Weltersbach ◽  
Harry V. Strehlow
Keyword(s):  
Baltic Sea ◽  
Gadus Morhua ◽  
Sublethal Effects ◽  
Atlantic Cod ◽  
Control Fish ◽  
Recreational Fisheries ◽  
Release Rates ◽  
Release Process ◽  
Catch And Release ◽  
Recreational Fishery

Abstract Weltersbach, M. S., and Strehlow, H. V. 2013. Dead or alive—estimating post-release mortality of Atlantic cod in the recreational fishery. – ICES Journal of Marine Science, 70: 864–872. Atlantic cod (Gadus morhua) is one of the most important commercial and recreational target species in European marine waters. Recent recreational fisheries surveys revealed that recreational cod catches and release rates are substantial compared to the commercial fishery, particularly in the western Baltic Sea. Despite high release rates, no literature exists exploring the post-release mortality of cod and potential sublethal effects after catch-and-release in recreational fisheries. This study investigates (i) the post-release mortality of undersized cod, (ii) potential factors affecting mortality, and (iii) consequences of the catch-and-release process on cod. During four experimental trials, western Baltic Sea cod were angled from a charter vessel and thereafter observed together with control fish in netpens for 10 d at holding temperatures between 6.2 and 19.8°C. Adjusted mortality rates for angled cod ranged from 0.0–27.3% (overall mean 11.2%). A logistic regression analysis revealed that bleeding and holding-water temperature were the only significant predictors of mortality. Slow hook injury healing (>10 d) and bacterial wound infections were observed in some surviving cod. The results will help to increase the accuracy of recreational cod removal estimates and thereby improve the management of western Baltic cod stock.

Catch and Release in Marine Recreational Fisheries

2002 ◽  
Keyword(s):  
Mortality Rate ◽  
Potential Benefit ◽  
Stock Assessment ◽  
The United States ◽  
Natural Mortality ◽  
Release Process ◽  
Catch And Release ◽  
Simulation Techniques ◽  
Longline Fisheries ◽  
Tag Shedding

<em>Abstract.</em>—Most billfish caught by recreational and U.S. longline fishermen are returned to the sea and, because of their overfished status, the United States has urged that all live billfish taken in Atlantic longline fisheries be released. Knowledge of the proportion of these fish that die due to the catch-and-release process, is important both for stock assessment, and to know the potential benefit of releasing fish taken as bycatch in commercial fisheries. Existing information indicates that the magnitude of this mortality is low, but comes from a limited number of studies using small numbers of ultrasonic tags. Recent technology that uses tags that release from the fish after a preprogrammed time, and then transmit data to satellites, offers the potential for developing better estimates of release mortality. This paper uses simulation techniques to examine factors leading to robust estimates of release mortality. Most sources of error in tagging experiments will lead to upward bias in the estimates. These include tag failure, tagging induced mortality, natural mortality, and tag shedding. Given the importance of the estimate to future billfish management, initial studies should focus on proving the technology. Tag failures produce ambiguous results and should be minimized, to the extent possible, or eliminated from the analysis where appropriate. Under perfect conditions (no tag failure, no tag induced mortality, and no tag shedding), individual experiments should apply a minimum of about 100 tags. The length of time from tagging until the tag releases from the fish should only be long enough for the catch-and-release mortality to be fully expressed. Because each fishing mode is likely to have a different release mortality rate, each experiment only estimates the release mortality rate for the species, gear, and fishing method employed in the fishery studied. The number of tags required to estimate the total number of deaths of released fish, of all species, could be in the tens of thousands. However, a well-researched experimental design might reduce the required number of tags significantly.

Satiation in humans is modulated by fatty acid chain length

2001 ◽  
Vol 120 (5) ◽  
pp. A710-A710
Author(s):  
S LAL ◽  
J MCLAUGHLIN ◽  
O NIAZ ◽  
G DOCKRAY ◽  
A VARRO ◽  
...  
Keyword(s):  
Fatty Acid ◽  
Chain Length ◽  
Fatty Acid Chain Length ◽  
Fatty Acid Chain

Direct Observation of Chain Lengths and Conformations in Oligofluorene Distributions from Controlled Polymerization by Double Electron-Electron Resonance

2019 ◽  
Author(s):  
Dennis Bücker ◽  
Annika Sickinger ◽  
Julian D. Ruiz Perez ◽  
Manuel Oestringer ◽  
Stefan Mecking ◽  
...  
Keyword(s):  
Chain Length ◽  
Length Distribution ◽  
Catalyst System ◽  
Chain Conformation ◽  
Controlled Polymerization ◽  
Chain Length Distribution ◽  
Electron Resonance ◽  
Double Electron ◽  
The Individual ◽  
Double Electron Electron Resonance

Synthetic polymers are mixtures of different length chains, and their chain length and chain conformation is often experimentally characterized by ensemble averages. We demonstrate that Double-Electron-Electron-Resonance (DEER) spectroscopy can reveal the chain length distribution, and chain conformation and flexibility of the individual n-mers in oligo-(9,9-dioctylfluorene) from controlled Suzuki-Miyaura Coupling Polymerization (cSMCP). The required spin-labeled chain ends were introduced efficiently via a TEMPO-substituted initiator and chain terminating agent, respectively, with an in situ catalyst system. Individual precise chain length oligomers as reference materials were obtained by a stepwise approach. Chain length distribution, chain conformation and flexibility can also be accessed within poly(fluorene) nanoparticles.

Mechanisms of Drug Solubilization by Polar Lipids in Biorelevant Media

2020 ◽  
Author(s):  
Vladimir Katev ◽  
Zahari Vinarov ◽  
Slavka S. Tcholakova
Keyword(s):  
Chain Length ◽  
Acyl Chain ◽  
Polar Lipids ◽  
Superior Performance ◽  
Head Group ◽  
Formulation Development ◽  
Biorelevant Media ◽  
Drug Solubilization ◽  
Colloidal Aggregates ◽  
Class 1

Despite the widespread use of lipid excipients in both academic research and oral formulation development, rational selection guidelines are still missing. In the current study, we aimed to establish a link between the molecular structure of commonly used polar lipids and drug solubilization in biorelevant media. We studied the effect of 26 polar lipids of the fatty acid, phospholipid or monoglyceride type on the solubilization of fenofibrate in a two-stage <i>in vitro</i> GI tract model. The main trends were checked also with progesterone and danazol.<br>Based on their fenofibrate solubilization efficiency, the polar lipids can be grouped in 3 main classes. Class 1 substances (n = 5) provide biggest enhancement of drug solubilization (>10-fold) and are composed only by unsaturated compounds. Class 2 materials (n = 10) have an intermediate effect (3-10 fold increase) and are composed primarily (80 %) of saturated compounds. Class 3 materials (n = 11) have very low or no effect on drug solubilization and are entirely composed of saturated compounds.<br>The observed behaviour of the polar lipids was rationalized by using two classical physicochemical parameters: the acyl chain phase transition temperature (<i>T</i><sub>m</sub>) and the critical micellar concentration (CMC). Hence, the superior performance of class 1 polar lipids was explained by the double bonds in their acyl chains, which: (1) significantly decrease <i>T</i><sub>m</sub>, allowing these C18 lipids to form colloidal aggregates and (2) prevent tight packing of the molecules in the aggregates, resulting in bigger volume available for drug solubilization. Long-chain (C18) saturated polar lipids had no significant effect on drug solubilization because their <i>T</i><sub>m</sub> was much higher than the temperature of the experiment (<i>T</i> = 37 C) and, therefore, their association in colloidal aggregates was limited. On the other end of the spectrum, the short chain octanoic acid manifested a high CMC (50 mM), which had to be exceeded in order to enhance drug solubilization. When these two parameters were satisfied (C > CMC, <i>T</i><sub>m</sub> < <i>T</i><sub>exp</sub>), the increase of the polar lipid chain length increased the drug solubilization capacity (similarly to classical surfactants), due to the decreased CMC and bigger volume available for solubilization.<br>The hydrophilic head group also has a dramatic impact on the drug solubilization enhancement, with polar lipids performance decreasing in the order: choline phospholipids > monoglycerides > fatty acids.<br>As both the acyl chain length and the head group type are structural features of the polar lipids, and not of the solubilized drugs, the impact of <i>T</i><sub>m</sub> and CMC on solubilization by polar lipids should hold true for a wide variety of hydrophobic molecules. The obtained mechanistic insights can guide rational drug formulation development and thus support modern drug discovery pipelines.<br>

Mechanisms of Drug Solubilization by Polar Lipids in Biorelevant Media

2020 ◽  
Author(s):  
Vladimir Katev ◽  
Zahari Vinarov ◽  
Slavka S. Tcholakova
Keyword(s):  
Chain Length ◽  
Acyl Chain ◽  
Polar Lipids ◽  
Superior Performance ◽  
Head Group ◽  
Formulation Development ◽  
Biorelevant Media ◽  
Drug Solubilization ◽  
Colloidal Aggregates ◽  
Class 1

Despite the widespread use of lipid excipients in both academic research and oral formulation development, rational selection guidelines are still missing. In the current study, we aimed to establish a link between the molecular structure of commonly used polar lipids and drug solubilization in biorelevant media. We studied the effect of 26 polar lipids of the fatty acid, phospholipid or monoglyceride type on the solubilization of fenofibrate in a two-stage <i>in vitro</i> GI tract model. The main trends were checked also with progesterone and danazol.<br>Based on their fenofibrate solubilization efficiency, the polar lipids can be grouped in 3 main classes. Class 1 substances (n = 5) provide biggest enhancement of drug solubilization (>10-fold) and are composed only by unsaturated compounds. Class 2 materials (n = 10) have an intermediate effect (3-10 fold increase) and are composed primarily (80 %) of saturated compounds. Class 3 materials (n = 11) have very low or no effect on drug solubilization and are entirely composed of saturated compounds.<br>The observed behaviour of the polar lipids was rationalized by using two classical physicochemical parameters: the acyl chain phase transition temperature (<i>T</i><sub>m</sub>) and the critical micellar concentration (CMC). Hence, the superior performance of class 1 polar lipids was explained by the double bonds in their acyl chains, which: (1) significantly decrease <i>T</i><sub>m</sub>, allowing these C18 lipids to form colloidal aggregates and (2) prevent tight packing of the molecules in the aggregates, resulting in bigger volume available for drug solubilization. Long-chain (C18) saturated polar lipids had no significant effect on drug solubilization because their <i>T</i><sub>m</sub> was much higher than the temperature of the experiment (<i>T</i> = 37 C) and, therefore, their association in colloidal aggregates was limited. On the other end of the spectrum, the short chain octanoic acid manifested a high CMC (50 mM), which had to be exceeded in order to enhance drug solubilization. When these two parameters were satisfied (C > CMC, <i>T</i><sub>m</sub> < <i>T</i><sub>exp</sub>), the increase of the polar lipid chain length increased the drug solubilization capacity (similarly to classical surfactants), due to the decreased CMC and bigger volume available for solubilization.<br>The hydrophilic head group also has a dramatic impact on the drug solubilization enhancement, with polar lipids performance decreasing in the order: choline phospholipids > monoglycerides > fatty acids.<br>As both the acyl chain length and the head group type are structural features of the polar lipids, and not of the solubilized drugs, the impact of <i>T</i><sub>m</sub> and CMC on solubilization by polar lipids should hold true for a wide variety of hydrophobic molecules. The obtained mechanistic insights can guide rational drug formulation development and thus support modern drug discovery pipelines.<br>

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