Tomas Fiala

Last Name

Fiala

First Name

Tomas

ORCID

0000-0001-6949-4561

Organisational unit

03940 - Wennemers, Helma / Wennemers, Helma

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Publications 1 - 10 of 11

Self-Sorting Collagen Heterotrimers
Islami, Valdrin; Bittner, Philipp; Fiala, Tomas; et al. (2024)
Journal of the American Chemical Society
Nature uses elaborate methods to control protein assembly, including that of heterotrimeric collagen. Here, we established design principles for the composition and register-selective assembly of synthetic collagen heterotrimers. The assembly code enabled the self-sorting of eight different strands into three─out of 512 possible─triple helices via complementary (4S)-aminoproline and aspartate residues. Native ESI-MS corroborated the specific assembly into coexisting heterotrimers.
The Yin and Yang of How N-Terminal Acyl Caps Affect Collagen Triple Helices
Fiala, Tomas; Heeb, Rahel; Vigliotti, Luca; et al. (2023)
Biomacromolecules
N-terminal acylation is a common tool for the installationof functionalmoieties (e.g., sensors or bioactive molecules) on collagen modelpeptides (CMPs). The N-acyl group and its lengthare generally assumed to have little or no influence on the propertiesof the collagen triple helix formed by the CMP. Here, we show thatthe length of short (C-1-C-4) acyl cappinggroups has different effects on the thermal stability of collagentriple helices in POG, OGP, and GPO frames. While the effect of differentcapping groups on the stability of triple helices in the GPO frameis negligible, longer acyl chains stabilize OGP triple helices butdestabilize POG analogues. The observed trends arise from a combinationof steric repulsion, the hydrophobic effect, and n -> pi* interactions. Our study provides a basis for thedesign of N-terminally functionalized CMPs with predictable effectson triple helix stability.
Seeing the Spikes: The Future of Targetable Synthetic Voltage Sensors
Fiala, Tomas; Sulzer, David; Sames, Dalibor (2025)
ACS Chemical Neuroscience
Measuring the transduction of electrical signals within neurons is a key capability in neuroscience. Fluorescent voltage sensitive dyes (VSDs) were early tools that complemented classical electrophysiology by enabling the optical recording of membrane potential changes from many cells simultaneously. Recent advances in the VSD field have led to bright and highly sensitive sensors that can be targeted to the desired cell populations in live brain tissue. Despite this progress, recently, protein-based genetically encoded voltage indicators (GEVIs) have become the go-to tools for targeted voltage imaging in complex environments. In this Perspective, we summarize progress in developing targetable VSDs, discuss areas where these synthetic sensors are or could become relevant, and outline hurdles that need to be overcome to promote the routine use of targetable VSDs in neuroscience research.
Molecular Design of SERTlight: A Fluorescent Serotonin Probe for Neuronal Labeling in the Brain
Lee, Wei-Li; Westergaard, Xavier; Hwu, Christopher; et al. (2024)
Journal of the American Chemical Society
The serotonergic transmitter system plays fundamental roles in the nervous system in neurotransmission, synaptic plasticity, pathological processes, and therapeutic effects of antidepressants and psychedelics, as well as in the gastrointestinal and circulatory systems. We introduce a novel small molecule fluorescent agent, termed SERTlight, that specifically labels serotonergic neuronal cell bodies, dendrites, and axonal projections as a serotonin transporter (SERT) fluorescent substrate. SERTlight was developed by an iterative molecular design process, based on an aminoethyl-quinolone system, to integrate structural elements that impart SERT substrate activity, sufficient fluorescent brightness, and a broad absence of pharmacological activity, including at serotonin (5-hydroxytryptamine, 5HT) receptors, other G protein-coupled receptors (GPCRs), ion channels, and monoamine transporters. The high labeling selectivity is not achieved by high affinity binding to SERT itself but rather by a sufficient rate of SERT-mediated transport of SERTlight, resulting in accumulation of these molecules in 5HT neurons and yielding a robust and selective optical signal in the mammalian brain. SERTlight provides a stable signal, as it is not released via exocytosis nor by reverse SERT transport induced by 5HT releasers such as MDMA. SERTlight is optically, pharmacologically, and operationally orthogonal to a wide range of genetically encoded sensors, enabling multiplexed imaging. SERTlight enables labeling of distal 5HT axonal projections and simultaneous imaging of the release of endogenous 5HT using the GRAB5HT sensor, providing a new versatile molecular tool for the study of the serotonergic system.
Carbohydrate Co-Solutes Stabilize Collagen Triple Helices
Nomura, Kota; Fiala, Tomas; Wennemers, Helma (2024)
ChemBioChem
Carbohydrates are common co-solutes for the stabilization of proteins. The effect of carbohydrate solutions on the stability of collagen, the most abundant protein in mammals, is, however, underexplored. In this work, we studied the thermal stability of collagen triple helices derived from a molecularly defined collagen model peptide (CMP), Ac-(Pro-Hyp-Gly)₇-NH₂, in solutions of six common mono- and disaccharides. We show that the carbohydrates stabilize the collagen triple helix in a concentration-dependent manner, with an increase of the melting temperature of up to 17 °C. In addition, we show that the stabilizing effect is similar for all studied sugars, including trehalose, which is otherwise considered a privileged bioprotectant. The results provided insight into the effects of sugar co-solutes on collagen triple helices and can aid the selection of storage environments for collagen-based materials and probes.
Frame Shifts Affect the Stability of Collagen Triple Helices
Fiala, Tomas; Barros, Emília P.; Ebert, Marc-Olivier; et al. (2022)
Journal of the American Chemical Society
Collagen model peptides (CMPs), composed of proline–(2S,4R)-hydroxyproline–glycine (POG) repeat units, have been extensively used to study the structure and stability of triple-helical collagen – the dominant structural protein in mammals – at the molecular level. Despite the more than 50-year history of CMPs and numerous studies on the relationship between the composition of single-stranded CMPs and the thermal stability of the assembled triple helices, little attention has been paid to the effects arising from their terminal residues. Here, we show that frame-shifted CMPs, which share POG repeat units but terminate with P, O, or G, form triple helices with vastly different thermal stabilities. A melting temperature difference as high as 16 °C was found for triple helices from 20-mers Ac-OG[POG]6-NH2 and Ac-[POG]6PO-NH2 and triple helices of the constitutional isomers Ac-[POG]7-NH2 and Ac-[GPO]7-NH2 melt 10 °C apart. A combination of thermal denaturation, CD and NMR spectroscopic studies, and molecular dynamics simulations revealed that the stability differences originate from the propensity of the peptide termini to preorganize into a polyproline-II helical structure. Our results advise that care must be taken when designing peptide mimics of structural proteins as subtle changes in the terminal residues can significantly affect their properties. Our findings also provide a general and straightforward tool for tuning the stability of CMPs for applications as synthetic materials and biological probes.
The irreplaceable Glycine: Glycine homologs destabilize the collagen triple helix
Kodr, David; Fiala, Tomas; Wennemers, Helma (2024)
Tetrahedron Letters
Collagen, the most widespread protein in animals, contains glycine as every third amino acid. This regular repetition of glycine residues is required for the tight packing of the collagen triple helix. In this work, we substitute glycine with its homolog β-alanine in collagen model peptides (CMPs) and study the effect of β-alanine on the formation of triple helices. While β-alanine in the middle of CMP sequences is incompatible with triple helix formation, terminal β-alanine residues are tolerated. The work highlights the critical role of glycine in collagen.
Chemical Targeting of Rhodol Voltage-Sensitive Dyes to Dopaminergic Neurons
Fiala, Tomas; Mosharov, Eugene V.; Wang, Jihang; et al. (2022)
ACS Chemical Neuroscience
Optical imaging of changes in the membrane potential of living cells can be achieved by means of fluorescent voltage-sensitive dyes (VSDs). A particularly challenging task is to efficiently deliver these highly lipophilic probes to specific neuronal subpopulations in brain tissue. We have tackled this task by designing a solubilizing, hydrophilic polymer platform that carries a high-affinity ligand for a membrane protein marker of interest and a fluorescent VSD. Here, we disclose an improved design of polymer-supported probes for chemical, nongenetic targeting of voltage sensors to axons natively expressing the dopamine transporter in ex vivo mouse brain tissue. We first show that for negatively charged rhodol VSDs functioning on the photoinduced electron transfer principle, poly(ethylene glycol) as a carrier enables targeting with higher selectivity than the polysaccharide dextran in HEK cell culture. In the same experimental setting, we also demonstrate that incorporation of an azetidine ring into the rhodol chromophore substantially increases the brightness and voltage sensitivity of the respective VSD. We show that the superior properties of the optimized sensor are transferable to recording of electrically evoked activity from dopaminergic axons in mouse striatal slices after averaging of multiple trials. Finally, we suggest the next milestones for the field to achieve single-scan recordings with nongenetically targeted VSDs in native brain tissue.
Site selective C–H functionalization of Mitragyna alkaloids reveals a molecular switch for tuning opioid receptor signaling efficacy
Bhowmik, Srijita; Galeta, Juraj; Havel, Václav; et al. (2021)
Nature Communications
Mitragynine (MG) is the most abundant alkaloid component of the psychoactive plant material “kratom”, which according to numerous anecdotal reports shows efficacy in self-medication for pain syndromes, depression, anxiety, and substance use disorders. We have developed a synthetic method for selective functionalization of the unexplored C11 position of the MG scaffold (C6 position in indole numbering) via the use of an indole-ethylene glycol adduct and subsequent iridium-catalyzed borylation. Through this work we discover that C11 represents a key locant for fine-tuning opioid receptor signaling efficacy. 7-Hydroxymitragynine (7OH), the parent compound with low efficacy on par with buprenorphine, is transformed to an even lower efficacy agonist by introducing a fluorine substituent in this position (11-F-7OH), as demonstrated in vitro at both mouse and human mu opioid receptors (mMOR/hMOR) and in vivo in mouse analgesia tests. Low efficacy opioid agonists are of high interest as candidates for generating safer opioid medications with mitigated adverse effects.
Predicting Collagen Triple Helix Stability through Additive Effects of Terminal Residues and Caps
Fiala, Tomas; Barros, Emilia P.; Heeb, Rahel; et al. (2023)
Angewandte Chemie. International Edition
Collagen model peptides (CMPs) consisting of proline-(2S,4R)-hydroxyproline-glycine (POG) repeats have provided a breadth of knowledge of the triple helical structure of collagen, the most abundant protein in mammals. Predictive tools for triple helix stability have, however, lagged behind since the effect of CMPs with different frames ([POG](n), [OGP](n), or [GPO](n)) and capped or uncapped termini have so far been underestimated. Here, we elucidated the impact of the frame, terminal functional group and its charge on the stability of collagen triple helices. Combined experimental and theoretical studies with frame-shifted, capped and uncapped CMPs revealed that electrostatic interactions, strand preorganization, interstrand H-bonding, and steric repulsion at the termini contribute to triple helix stability. We show that these individual contributions are additive and allow for the prediction of the melting temperatures of CMP trimers.

Publications 1 - 10 of 11

Tomas Fiala

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