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101.
Dr. Tomasz Badowski Ewa P. Gajewska Karol Molga Prof. Bartosz A. Grzybowski 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(2):735-740
When computers plan multistep syntheses, they can rely either on expert knowledge or information machine-extracted from large reaction repositories. Both approaches suffer from imperfect functions evaluating reaction choices: expert functions are heuristics based on chemical intuition, whereas machine learning (ML) relies on neural networks (NNs) that can make meaningful predictions only about popular reaction types. This paper shows that expert and ML approaches can be synergistic—specifically, when NNs are trained on literature data matched onto high-quality, expert-coded reaction rules, they achieve higher synthetic accuracy than either of the methods alone and, importantly, can also handle rare/specialized reaction types. 相似文献
102.
Nir Sukenik Francesco Tassinari Shira Yochelis Oded Millo Lech Tomasz Baczewski Yossi Paltiel 《Molecules (Basel, Switzerland)》2020,25(24)
The spin–spin interactions between chiral molecules and ferromagnetic metals were found to be strongly affected by the chiral induced spin selectivity effect. Previous works unraveled two complementary phenomena: magnetization reorientation of ferromagnetic thin film upon adsorption of chiral molecules and different interaction rate of opposite enantiomers with a magnetic substrate. These phenomena were all observed when the easy axis of the ferromagnet was out of plane. In this work, the effects of the ferromagnetic easy axis direction, on both the chiral molecular monolayer tilt angle and the magnetization reorientation of the magnetic substrate, are studied using magnetic force microscopy. We have also studied the effect of an applied external magnetic field during the adsorption process. Our results show a clear correlation between the ferromagnetic layer easy axis direction and the tilt angle of the bonded molecules. This tilt angle was found to be larger for an in plane easy axis as compared to an out of plane easy axis. Adsorption under external magnetic field shows that magnetization reorientation occurs also after the adsorption event. These findings show that the interaction between chiral molecules and ferromagnetic layers stabilizes the magnetic reorientation, even after the adsorption, and strongly depends on the anisotropy of the magnetic substrate. This unique behavior is important for developing enantiomer separation techniques using magnetic substrates. 相似文献
103.
Ivan Liakh Tomasz Sledzinski Lukasz Kaska Paulina Mozolewska Adriana Mika 《Molecules (Basel, Switzerland)》2020,25(22)
Obesity is associated with alterations in the composition and amounts of lipids. Lipids have over 1.7 million representatives. Most lipid groups differ in composition, properties and chemical structure. These small molecules control various metabolic pathways, determine the metabolism of other compounds and are substrates for the syntheses of different derivatives. Recently, lipidomics has become an important branch of medical/clinical sciences similar to proteomics and genomics. Due to the much higher lipid accumulation in obese patients and many alterations in the compositions of various groups of lipids, the methods used for sample preparations for lipidomic studies of samples from obese subjects sometimes have to be modified. Appropriate sample preparation methods allow for the identification of a wide range of analytes by advanced analytical methods, including mass spectrometry. This is especially the case in studies with obese subjects, as the amounts of some lipids are much higher, others are present in trace amounts, and obese subjects have some specific alterations of the lipid profile. As a result, it is best to use a method previously tested on samples from obese subjects. However, most of these methods can be also used in healthy, nonobese subjects or patients with other dyslipidemias. This review is an overview of sample preparation methods for analysis as one of the major critical steps in the overall analytical procedure. 相似文献
104.
Dr. Adam Mames Dariusz Gołowicz Dr. Mariusz Pietrzak Dr. Krzysztof Kazimierczuk Prof. Sławomir Szymański Dr. Tomasz Ratajczyk 《Chemphyschem》2020,21(6):540-545
Triptycene derivatives are widely utilized in different fields of chemistry and materials sciences. Their physicochemical properties, often of pivotal importance for the rational design of triptycene-based functional materials, are influenced by noncovalent interactions between substituents mounted on the triptycene skeleton. Herein, a unique interaction between electron-rich substituents in the peri position and the silyl group located on the bridgehead sp3-carbon is discussed on the example of 1,4-dichloro-9-(p-methoxyphenyl)-silyltriptycene (TRPCl) which exists in solution in the form of two rotamers differing by dispositions, syn or anti, of the Si−CPh (the CPh atom is from the p-methoxyphenyl group) bond against the peri-Cl atom. For the first time, substantial differences between the Si−CPh bonds in these two dispositions are identified, based on indirect experimental and direct theoretical evidence. For these two orientations, the experimental 1J(Si,CPh) values differ by as much as 10 percent. The differences are explained in terms of effective electron density transfer from the peri-Cl atom to the antibonding σ* orbitals of the Si−X bonds (X=H, CPh) oriented anti to that atom. The electronic effects are revealed by an NBO analysis. Connections of these observations with the notion of blue-shifting hydrogen bonds are discussed. 相似文献
105.
Two 3-silanyl-propenylphosphonate esters ( 1a , 1b ) were synthesized, and their deprotonation was attempted using RONa/ROH, RLi/THF, and LDA/THF systems. In the first two cases, the nucleophilic addition was the predominant (or exclusive) reaction observed; deprotonation was achieved with LDA, as confirmed by the reaction of the lithiated species with alkylating agents and with benzaldehyde. Chemical behavior of substrates 1 does not parallel closely that of the parent silanyl or phosphoryl-substituted allylic systems. © John Wiley & Sons, Inc. 相似文献
106.
Reaction between O,O-diethyl-S-phenyl phosphorothiolate and lithium dialkylamides results in the displacement of the PhS substituent by the R2N group. With Grignard reagents, the same substrate gives products of the nucleophilic substitution at both the phosphorus and the sulfur atom. 相似文献
107.
Tomasz Bujak Martyna Zagrska-Dziok Aleksandra Ziemlewska Zofia Nizio-ukaszewska Kamila Lal Tomasz Wasilewski Zofia Hordyjewicz-Baran 《Molecules (Basel, Switzerland)》2022,27(3)
Flowers are a natural source of bioactive compounds that not only have antioxidant, anti-inflammatory, and anti-aging properties, but can also be used as natural dyes. For this reason, nowadays plants are widely used to produce natural cosmetics and foods. In these studies, the properties of the water extracts of Papaver rhoeas L., Punica granatum L., Clitoria ternatea L., Carthamus tinctorius L., and Gomphrena globosa L., as bioactive, natural dyes, were investigated. Plant flower extracts were tested for their antioxidant (ABTS and DPPH radical methods) and anti-inflammatory effects by determining the ability to inhibit the activity of lipoxygenase and proteinase. The extracts were tested for their cytotoxic effect on skin cells, using Alamar Blue and Neutral Red tests. The ability to inhibit the activity of enzymes responsible for the destruction of elastin and collagen was also studied. Research has shown that extracts have no toxic effect on skin cells, are a rich source of antioxidants and show the ability to inhibit the activity of elastase and collagenase enzymes. P. rhoeas extract showed the strongest antioxidant properties with IC50 value of 24.8 ± 0.42 µg/mL and 47.5 ± 1.01 µg/mL in ABTS and DPPH tests, respectively. The tested plants are also characterized by an anti-inflammatory property, for which the ability to inhibit lipoxygenase at a level above 80% and proteinase at the level of about 55% was noted. Extracts from P. rhoeas, C. ternatea, and C. tinctorius show the strongest coloring ability and can permanently dye cosmetic products, without significant color changes during the storage of the product. 相似文献
108.
109.
Magorzata Kapelko-eberska Marta Meisel Krzysztof Buksa Artur Gryszkin Antoni Szumny Bogna Latacz Bartosz Raszewski Tomasz Ziba 《Molecules (Basel, Switzerland)》2022,27(8)
The present study aimed to determine changes in the properties of starch triggered by its long-lasting (1, 2, 4, 7, 10, or 14 days) retention with citric acid (5 g/100 g) at a temperature of 40 °C. The starch citrates obtained under laboratory conditions had a low degree of substitution, as confirmed via NMR and HPSEC analyses. The prolonging time of starch retention with citric acid at 40 °C contributed to its increased esterification degree (0.05–0.11 g/100 g), swelling power (30–38 g/g), and solubility in water (19–35%) as well as to decreased viscosity of the starch pastes. Starch heating with citric acid under the applied laboratory conditions did not affect the course of DSC thermal characteristics of starch pasting. The low-substituted starch citrates exhibited approximately 15% resistance to amylolysis. 相似文献
110.
Simple-structured, well-functioned disposable poly(dimethylsiloxane) (PDMS) microchips were developed for capillary isoelectric focusing with whole column imaging detection (CIEF-WCID). Side-by-side comparison of the developed microchips with well-established commercial capillary cartridges demonstrated that the disposable microchips have comparable performance as well as advantages such as absence of lens effect and possibility of high-aspect-ratio accompanied with a dramatic reduction in cost. 相似文献