The effect of temperature on the effectiveness of the incorporation of deuterium into pyrrolylcarnosine (PC) was studied. Deuterium gas and heavy water were used as a source of deuterium. Isotope ...exchange was carried out using solid-phase and liquid-phase methods. It was found that it is better to use isotope exchange with deuterated water to obtain preparative amounts of labeled pyrrolylcarnosine. When using y solid-phase method, the main label is in pyrrole. The incorporation of deuterium at a higher temperature occurs more evenly. In addition, the use of deuterated water made it possible to reduce the amount of unlabeled isotopomer to almost 0% and to obtain a product with a yield of 70% and a content of more than seven deuterium atoms. It was established that the content of deuterium in the compound can be increased by pretreating the reaction mixture with deuterium gas. This approach opens up additional opportunities for the synthesis of labeled compounds.
Various methods of introducing deuterium into dopamine using isotope exchange are considered. The best result is achieved by isotope exchange with deuterated water at 190°C for 30 min using (a) ...trifluoroacetic acid as a catalyst and (b) 5% Pd/Al
2
O
3
catalyst presaturated with deuterium gas. In the first case, the yield of deuterated dopamine was 65–70%, and the average deuterium content was 2.4–2.5 at./molecule. In the second case, the yield decreased to 35–40%, but the deuterium content increased to 3.50–3.60 at./molecule. The obtained result highlights the effectiveness of an integrated approach to introducing hydrogen isotopes into organic molecules, when activated hydrogen isotope species are formed on the catalyst and the substance deposited on it, which contribute to increasing the efficiency of isotope exchange with deuterated water at heating.
The cytotoxicity of doxorubicin (Dox) and its peptide modifications Z-Gly-Pro-Dox and Boc-Gly-Pro-Dox were studied.
Tetrahymena pyriformis
was used as a test system, which made it possible, due to ...the short life cycle and high reproduction rate of ciliates, to trace their response to the effects of toxicants over several generations. It was found that peptide modification of the Dox molecule markedly reduces its cytotoxic and cytostatic effect. The Z-Gly-Pro-Dox modification has less cytotoxic and cytostatic effect compared to Boc-Gly-Pro-Dox. When determining the ability of drugs (at a concentration of 100 μM) to prevent bacterial contamination of samples, it was shown that the smallest degree of overgrowth was recorded in the presence of Dox (OD
600nm
81.1). Boc-Gly-Pro-Dox also had a bacteriostatic effect, though less pronounced (OD
600nm
93.8). The degree of overgrowth in the presence of Z-Gly-Pro-Dox was close to that of distilled water. The results obtained on ciliates did not contradict the data obtained in similar studies on mice.
The conditions for introducing deuterium into Trp-Pro-Pro-Trp and Boc-Trp-Pro-Pro-Trp by isotope exchange with D
2
O in the presence of a 5% Pd/Al
2
O
3
catalyst were developed. The thermal stability ...of Trp-Pro-Pro-Trp upon introduction of deuterium was significantly lower than that of the Boc-protected peptide. The yield of deuterated Trp-Pro-Pro-Trp did not exceed 10–15%, and the inclusion of deuterium was about 0.9–1.1 at./molecule at 125°C. The introduction of deuterium into Boc-Trp-Pro-Pro-Trp was possible at 150°C, which increased the deuterium content to 3.75 at./molecule. It was found that the tryptophan fragment of the molecule contains approximately 2 times more deuterium than the proline fragment. It was found that pretreatment of Boc-Trp-Pro-Pro-Trp with deuterium gas not only activates isotope exchange, but also promotes the removal of Boc protection. The data obtained indicate that the reason for this phenomenon is associated with the generation of deuterium cations on Boc-Trp-Pro-Pro-Trp molecules by the catalyst.
A mass spectrometric method has been developed for determining the content of dopamine and serotonin derivatives, which allows evaluating the efficiency of their penetration through artificial ...membranes depending on the structure of their peptide fragment. In this case, the diffusion of dopamine and serotonin derivatives through the membrane occurred as a result of competitive interactions. It was shown which compounds in this mixture more easily penetrate through artificial membranes. It was found that the most promising in terms of overcoming the BBB are Boc–Pro–Srt and Boc–Pro–DOPA.
The influence of various factors on the efficiency of introducing deuterium into 3-(
N
-pyrrolyl)-propanoyl-L-histidine and 3-(
N
-salicyl)-propanoyl-L-histidine was studied. Heavy water was used as ...a source of deuterium. It is shown that the content of deuterium atoms in the substance can be increased by pretreating the reaction mixture with deuterium gas. The new approach opens up additional possibilities both for obtaining high labeled pharmaceuticals by introducing hydrogen isotopes into organic compounds, and theoretically for a deeper understanding of the role in this process of activated deuterium or tritium particles solvated on the carrier and in the pool of matter.
Effect of temperature on the efficiency of deuterium introduction into a new biologically active compound salicylcarnosine (SC) has been studied. Gaseous deuterium and heavy water were used as ...deuterium sources. The synthesis of labelled SC by a solid-phase method at 190°C leads to formation of DSC in 53% yield and deuterium content about 4.8 atoms per molecule. It has been shown that isotope exchange between SC protons and deuterium water proceeds more efficiently after preliminary treatment of catalyst with gaseous deuterium at ambient temperature. DSC forms in 46% yield and contains about 7.3 deuterium atoms per molecule. The preparative synthesis of labelled SC by this procedure at 190°C results in DSC yield of 60–70% at deuterium content about 6.2 atoms per molecule. The new procedure for the activation of deuterium inclusion in peptides opens additional opportunities for preparing highly labelled compounds.
Objective:
The resistance of carnosine, pyrrolylcarnosine (PC) and salicylcarnosine (SC) to the action of leucine aminopeptidase and carboxypeptidases B and Y was evaluated.
Methods:
Proteolysis of ...carnosine and its derivatives under the action of leucine aminopeptidase, carboxypeptidases Y and B, or under the action of enzyme systems of plasma membranes of rat brain cells or blood plasma.
Results and Discussion:
It was found that proteolysis of carnosine, PC and SC under the action of leucine aminopeptidase does not occur. Carboxypeptidases B and Y, as well as the enzyme systems of blood plasma and plasma membranes of rat brain cells, degraded peptides containing β-alanyl,
N
-pyrrolyl,
N
-salicylic fragments to varying degrees. In all cases, histidine was formed. The formation of pyrrole or salicylic acid did not occur.
Conclusions:
It was found that carnosine, PC and SC showed high resistance to the action of amino- and carboxypeptidases in
in
vitro
experiments.
The efficiency of isotope exchange was compared when gaseous deuterium (solvent-free, solid-phase exchange) and deuterium water were employed as a deuterium source. It was established that exchange ...with deuterium water is preferable for producing labeled β-alanyl-L-histidine. When using the solid-phase method, the main part of the label is in histidine. The distribution of deuterium during isotope exchange with D
2
O is more uniform. In addition, the use of deuterium water makes it possible to reduce the amount of unlabeled isotopomer to 0.4% and receive a preparation with a yield of 40% (20 mg) and an average content of 3.6 deuterium atoms per carnosine molecule. It can be assumed that the high yield and greater incorporation of deuterium are associated with the pretreatment of the reaction mixture with gaseous deuterium.
The efficiency of incorporating deuterium into 4-aminobutanoic acid (GABA) has been studied. The use of D
2
O at 200°C makes it possible to introduce into GABA an average of about 0.5 deuterium ...atoms, D
2
O with trifluoroacetic acid (1 : 1) at 250°C, an average 1.49 deuterium atoms with a yield of 15%. The solid-phase method permits introducing about 3 deuterium atoms per GABA molecule. During isotopic exchange with D
2
O, the use of a palladium–rhodium mixture pretreated with deuterium gas made it possible to produce DGABA with the deuterium content of 4.5–4.6 atoms. But in both cases, the yields of DGABA were low. Preparative amounts of DGABA were produced engaging additional supports. The best result was obtained when applying GABA to zeolite. Using D
2
O with 5% Pd/BaSO
4
–GABA–zeolite pretreated with deuterium gas, allows producing DGABA with an average content of 1.5–2.0 deuterium atoms and a yield of about 30%.
