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Professor Radek Cibulka's laboratory has long been trying to develop systems that would facilitate chemical reactions, and thus the ways how to easily synthesize some drugs or other useful substances. The prestigious journal Chemical Science has now published a new system for chemical reductions based on deprotonated flavins, derivatives of vitamin B2. The system was developed as part of a collaboration between teams from the University of Chemical Technology, Prague and Adam Mickiewicz University within LA project from Czech Science Foundation and National Science Centre (Poland). "We feel like builders. Removing one component (a proton) from a molecule of almost colourless 3-methyllumichrome - a substance related to flavins - causes structural changes that lead to the formation of an orange flavin anion. This flavin anion is unique because its protonated form does not exist. Moreover, we used this anion as a catalyst for reductions. All you have to do is shine cyan light on it and the reduction takes place." says Radek Cibulka.<blockquote><h4>The original article</h4><h4><a target="_blank" rel="noopener noreferrer" href="https://pubs.rsc.org/en/content/articlelanding/2025/sc/d5sc01630d">Introduction of flavin anions into photoredox catalysis: acid–base equilibria of lumichrome allow photoreductions with an anion of an elusive 10-unsubstituted isoalloxazine</a></h4>Dorota Prukała, Ekaterina Zubova, Eva Svobodová, Ludmila Šimková, Naisargi Varma, Josef Chudoba, Jiří Ludvík, Gotard Burdzinski, Iwona Gulaczyk, Marek Sikorski and &nbsp;Radek CibulkaChem. Sci., 2025,16, 11255-11263<a target="_blank" rel="noopener noreferrer" href="https://doi.org/10.1039/D5SC01630D">https://doi.org/10.1039/D5SC01630D</a><h6>licensed under <a target="_blank" rel="noopener noreferrer" href="https://creativecommons.org/licenses/by/3.0/">CC-BY 3.0</a></h6></blockquote>Selected sections from the article follow. Formats and hyperlinks were adapted from the original.<h4>Abstract</h4>Flavins have been established as effective catalysts in oxidative photoredox catalysis. Conversely, their use in reductive photocatalysis remains limited, mainly due to the relatively low stability of the transient flavin radicals (semiquinones), which are used in photoreductions. The fully reduced forms of flavins are also disadvantaged in photocatalysis because they absorb light in the UV rather than in the visible region. In this work, we present a new approach for reductive flavin photocatalysis that utilises a flavin (isoalloxazine) anion derived from the elusive 10-unsubstituted 3,7,8-trimethylisoalloxazine, an unstable tautomer of 3-methyllumichrome. We found the conditions under which this isoalloxazine anion is formed by in situ deprotonation/isomerisation from the readily available 3-methyllumichrome and we subsequently used it as a photoredox catalyst in the reductive dehalogenation of activated bromoarenes and their C–P coupling reaction with trimethyl phosphite to form an arylphosphonate. Steady-state and transient absorption spectroscopy, NMR and cyclic voltammetry investigations, together with quantum chemical calculations, showed that the anion of oxidised isoalloxazine has several advantages, compared to other forms of flavins used in photoreductions, such as high stability, even in the presence of oxygen, an absorption maximum in the visible region, thereby allowing the use of excitation light between 470 and 505 nm, and a relatively long-lived singlet excited-state.<h4>Materials and methods</h4>Nuclear magnetic resonance (NMR) spectra were recorded in CD3CN, DMSOd6 , DMF-d6, TFA-d3 or in their mixtures on an Agilent 400-MR DDR2 (399.94 MHz for 1H, 100.58 MHz for 13C), JEOL-ECZL400G (400 MHz for 1H, 101 MHz for 13C), or Bruker Avance III 600 MHz (600 MHz for 1H and 151 MHz for 13C) at 298 K. Data for 1H NMR are reported as follows: chemical shift (δ ppm), multiplicity (s = singlet, d = doublet, t = triplet, q = quartet, m = multiplet, dd = doublet of doublets, dt = doublet of triplets, br = broad etc.), coupling constant (Hz), and integration. All NMR spectra were processed and assigned using MestreNova. High-resolution mass spectra were obtained on <a target="_blank" rel="noopener noreferrer" href="https://lcms.labrulez.com/library?mainauthorItems=5&amp;search=Q-Tof+Micro">Q-Tof Micro</a> (Waters), equipped with a quadrupole and time-of-flight (TOF) analyser and a multichannel plate (MCP) detector. GC-MS analysis were performed on gas chromatograph <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/library?mainauthorItems=3&amp;search=Trace+GC+Ultra">Trace Ultra</a> (Themo Scientific) with a quadrupole mass spectrometer <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/library?mainauthorItems=3&amp;search=DSQ+II">DSQ II</a> (Thermo Scientific) equipped with DB-5ms capillary column (30 m x 0.25mm, film 0,25 um) or on gas chromatograph <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/library?mainauthorItems=10&amp;search=7890">7890</a> (Agilent) with an <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/products/473">orbital trap mass spectrometer Exploris 240</a> (Thermo Scientific) equipped with DB-5ms capillary column (30 m x 0.25mm, film 0,25 um). <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/library?manufacturerItems=50&amp;search=SICRIT">SICRIT</a> (Soft Ionization by Chemical Reaction In Transfer - Plasmion GmbH, Germany) was used in positive mode. The melting points were measured on a Boetius melting point apparatus and are not corrected. Photoredox catalysis was performed using Luxeon Star LED 470 nm (65 lm @ 700mA) with dominant peak wavelengths 460–485 nm in tempered aluminium block (for arrangement, see S3) and Luxeon Star LED 505 nm (76 lm @ 350mA) with dominant peak wavelengths 490–515 nm. UV-Vis absorption spectra were recorded on a <a target="_blank" rel="noopener noreferrer" href="https://icpms.labrulez.com/library?mainauthorItems=1&amp;search=UV-2550">UV-2550</a> spectrophotometer (Schimadzu). Steady-state emission spectra and fluorescence excitation spectra were recorded on a Jobin Yvon-SpexFluorolog 3-22 spectrofluorometer. Note that spectra were recorded using the same excitation and emission slits for uniform spectral resolution and sensitivity. Fluorescence lifetime measurements of all compounds were performed using the time-correlated single-photon counting (TCSPC) method. Decays were measured with the TCSPC Triple Illuminator as an accessory for the Fluorologs 3-22 steady-state spectrofluorometer that adds lifetime-capability in the time domain. The excitation source were NanoLED diodes (λexc = 368 nm and 389 nm) from IBH. The instrument in this hardware configuration is capable of measuring lifetimes as short as 400 ps. Deconvolution of fluorescence decay curves was performed using IBH Consultants software. The experimental uncertainties in the lifetimes are 10 %. Setup for UV-Vis transient absorption spectra measurements: The triplet states were generated and analysed using laser flash photolysis employing a nanosecond Q-switched Nd: YAG laser in combination with an optical parametric oscillator (OPO) operating at 470 nm; the laser pulse energy was kept around 0.5 mJ/pulse. The sample's solution was deoxygenated by bubbling argon for 15 min before measurements. Spectra were determined using kinetics collected between 350–700nm with a 10 nm interval. See ref.1 for details. Electrochemical measurements(cyclic voltammetry) were managed by a computer driven potentiostat <a target="_blank" rel="noopener noreferrer" href="https://lcms.labrulez.com/library?search=PGSTAT101">PGSTAT101 </a>(Autolab-Metrohm) using NOVA 1.11 software, for details see Chapter 5.

Work of Professor Cibulka's team featured on the cover of Chemical Science journal

Fired cartridge cases are common evidence at shooting crime scenes. While fingerprints are often damaged and insufficient for identification, human scent traces may remain intact even after a gun is fired.In this pilot study, a simulated crime scene was created in which a volunteer loaded a weapon before firing. The scent remaining on fired cartridge cases was analyzed and compared to reference samples from several volunteers using olfactronics and olfactorics. Results suggest that scent analysis can support investigations by linking cartridge cases to the individual who handled the ammunition.<blockquote><h4>The original article</h4><h4><a target="_blank" rel="noopener noreferrer" href="https://pubs.acs.org/doi/10.1021/acs.analchem.4c06231">Analysis of the Human Scent on Fired Cartridge Cases from a Simulated Crime Scene</a></h4>Ulrika Malá*, Václav Vokálek, Pavel Vrbka, Jana Čechová, Petra Pojmanová, Oleksii Kaminskyi, Veronika Škeříková, Štěpán UrbanAnal. Chem. 2025, 97, 7, 3799–3803<a target="_blank" rel="noopener noreferrer" href="https://doi.org/10.1021/acs.analchem.4c06231">https://doi.org/10.1021/acs.analchem.4c06231</a><h6>licensed under <a target="_blank" rel="noopener noreferrer" href="https://creativecommons.org/licenses/by/4.0/">CC-BY 4.0</a></h6></blockquote>Selected sections from the article follow. Formats and hyperlinks were adapted from the original.Forensic olfactronics is a new field of forensic analysis whose aim is to analyze scent samples using advanced analytical chemistry techniques. <a href="javascript:void(0);">(1−3)</a> Unlike olfactorics (the odorology method using specially trained canines), forensic olfactronics is an objective method. On the other hand, the olfactory system of a canine is still more sensitive than the best contemporary instruments of analytical chemistry usable for human scent analysis. This is why both methods should be used for these purposes in the future during criminal investigations, so they can complement each other and be a desirable chain of evidence to present before the court. Cartridge cases are often one of the traces that can appear on the crime scenes usually connected with a shooting, mainly in the cases of very serious crimes. Unfortunately, the fingerprints tend to be partially spoiled; thus, they cannot be compared with the dactyloscopy database. In a previous study, <a href="javascript:void(0);">(4)</a> it was found that the less volatile substances that seem to be more significant for the individual identification of human scent <a href="javascript:void(0);">(5)</a> resist high temperatures for a short time (up to 500 °C for 1 min). That led to a presumption that at least a part of the human scent remaining on the cartridge after loading the gun and even after the gun’s firing would be sufficient for an individual identification. <a href="javascript:void(0);">(4)</a><h4>Experimental Section</h4><h5>Instrumentation</h5>For this experiment, only one gun type was used (a Sauer 38H, Sauer Sohn Germany, caliber 7.65 Browning, ammunition, type FMJ 73 grs, produced by Sellier Bellot, Czech Republic).The samples were measured by a <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/library?mainauthorItems=10&amp;search=7980B">7980B GC two-dimensional gas chromatograph</a> (Agilent, USA) coupled with a <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/library?mainauthorItems=24&amp;search=Pegasus+BT+4D">Pegasus BT 4D time-of-flight analyzer mass spectrometer</a> (LECO, USA). The columns were connected in reverse order. The primary column was a semipolar Rtx-200MS (30 m + 2 m precolumn, Restek, USA), and the secondary column was a nonpolar <a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/products/1745">TG5-HT</a> (1.1 m, Thermo Fisher Scientific, USA). The diameter of the columns was 0.25 mm, and the thickness of the stationary phase was 0.25 μm. Helium (purity 5.5, Linde CZ) was used as a carrier gas for gas chromatography. The sample was injected in a volume of 1 μL in splitless mode (2 min) at a temperature of 280 °C. The temperature gradient on the primary column started at 40 °C, held for 2 min, and ended at 320 °C, held for 10 min. The temperature increased at a rate of 5 °C/min. The temperature on the secondary column was always 5 °C higher than that on the primary column. The modulator between the two columns always had a temperature 15 °C higher than the secondary column. The cryogenic modulation at −80 °C with three modulation periods of 6, 8, and 10 s were used. The carrier gas flow rate was 1.5 mL/min. The interface between GC and MS was heated to 280 °C. The mass detector used electron ionization with an energy of 70 eV ionizing electrons, and the temperature of the ion source was 250 °C. Data collection took place in TIC (total ion current) mode, with a mass interval of 29–800 (m/z); data collection took place at a speed of 200 spectra/s. The time required to elute the solvent was set to 500 s. To increase the detection sensitivity, a 200 V higher voltage was set on the detector compared to tuning. The ratio of the signal and the noise was set at S/N 300.<h4>Results and Discussion</h4>By comparing the chromatograms of the scent samples collected on the original and the prewashed cartridges, significant differences supporting the necessity of the cleaning procedure before the collection itself were not found. The chromatogram area where the lubricant peaks were found was more concentrated on the original cartridges, but the differences were not significant. From a practical point of view, that is efficient for our experiments, as it gets closer to reality at the crime scene. Other experiments were carried out on nonprewashed ammunition based on these results.<named-content></named-content><named-content></named-content>Our olfactronic analysis showed successful individual separation/variance between different volunteers on the glass beads (see <a target="_blank" rel="noopener noreferrer" href="https://pubs.acs.org/doi/10.1021/acs.analchem.4c06231#fig3">Figure 3</a>). However, the system could not link the human scent extracted from the gun-fired cartridge cases to the volunteers. This could have been caused by the different kinds of background material that was provided by glass beads (see <a target="_blank" rel="noopener noreferrer" href="https://pubs.acs.org/doi/10.1021/acs.analchem.4c06231#fig1">Figure 1</a>) and cartridge cases (see <a target="_blank" rel="noopener noreferrer" href="https://pubs.acs.org/doi/10.1021/acs.analchem.4c06231#fig2">Figure 2</a>), despite the fact that data editing was done in an attempt to eliminate these differences. Another option could be that even if the significant substances for the identification withstand high temperatures, the explosion heat could slightly change them. Therefore, one of the solutions could be to equalize the conditions before the extraction by heating the glass beads to the same temperature to which the bullets are exposed when fired. Nevertheless, the surface differences from which the unknown trace was collected at the crime scene do not seem to play a significant role. This is important for further investigation, as the cartridge cases remaining at the crime scene could lay on many kinds of surfaces, and the analyses of the evidence must not depend on them. The inconsistency of the result from the previous experiment <a href="javascript:void(0);">(4)</a> where the cartridge cases were successfully linked to the volunteer who had loaded the gun before the shooting could be based on the fact that another mass spectrometer (Pegasus BT-4D) with new commercial software (ChromaTOF, version 5.51.06.0) was used for this experiment. The software having issues with processing the chromatograms (mainly peak areas) may have contributed to the inconsistency.<img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/Anal_Chem_2025_97_7_3799_3803_Figure_1_Chromatogram_of_a_volunteer_s_sample_from_our_small_database_captured_on_the_glass_beads_f34c95896c.jpg" alt="Anal. Chem. 2025, 97, 7, 3799–3803: Figure 1. Chromatogram of a volunteer’s sample from our small database captured on the glass beads. The x axis represents the retention time of the first column [s], and the y axis represents the retention time of the second column [s]. The areas corresponding to individual groups of substances are indicated in the image." srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_Anal_Chem_2025_97_7_3799_3803_Figure_1_Chromatogram_of_a_volunteer_s_sample_from_our_small_database_captured_on_the_glass_beads_f34c95896c.jpg 215w," sizes="100vw" width="2100" height="1524"><img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/Anal_Chem_2025_97_7_3799_3803_Figure_2_Chromatogram_of_an_unknown_sample_from_the_cartridge_case_736c975356.jpg" alt="Anal. Chem. 2025, 97, 7, 3799–3803: Figure 2. Chromatogram of an unknown sample from the cartridge case. The x axis represents the retention time of the first column [s]; the y axis represents the retention time of the second column [s]. The areas corresponding to individual groups of substances are indicated in the image." srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_Anal_Chem_2025_97_7_3799_3803_Figure_2_Chromatogram_of_an_unknown_sample_from_the_cartridge_case_736c975356.jpg 207w," sizes="100vw" width="2100" height="1577"><h4>Conclusions</h4>Two methods for comparing four scent traces from a simulated crime scene with 22 different volunteer scent samples were used. The aim was to find a certain volunteer who loaded the gun using eight analogous cartridges. Four samples of cartridge cases were then subjected to olfactronic analysis. These were collected from a heterogeneous crime scene. These four analogous samples were also compared by trained police canines. The olfactory method was successful and correctly identified the shooter. Both methods indicated that the surface (plastic sheet, wooden palette, and concrete floor) from which the scent traces were collected does not play a significant role in the identification. The results from the forensic olfactronic method showed the ability to distinguish each volunteer sampled on the glass beads; however, it has not yet been possible to link the fired cartridge cases to any of the volunteers. In the future, this problem can be eliminated by solving the problems with processing the peaks with commercial software that comes with the two-dimensional gas chromatograph. On the other hand, the issue could also be solved by equalizing the parameters on both surfaces (cartridge cases and glass beads) by heating the glass beads after the scent is collected on them. This heating would partly simulate the process of firing the gun.Additionally, olfactronic identification could also be complemented by a dactyloscopy comparison as well. Since both can be crucial for the investigation and together can form a desirable chain of evidence. The only question is in which order should the methods be used for the optimal analysis of both.The future prospects for the study include expanding the research to involve more volunteers and diversifying the types of weapons and ammunition tested. Additionally, further optimization of the sample preparation process is necessary, particularly to determine whether heating the glass beads to simulate gunfire can effectively link unknown samples to the shooter. Finally, addressing the issue of data alignment will be a critical step moving forward.

Analysis of the Human Scent on Fired Cartridge Cases from a Simulated Crime Scene

PAH Induction upon Pyrolysis of Hydroxyl-Terminated Polybutadiene-Based Solid Rocket Fuels

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