Friedjof Tellkamp

Capturing meta-stable conformations of enzymes and ligand complexes demands structural snapshots beyond static crystal structures. While time-resolved serial crystallography at room temperature, offers a time-resolution down to the femto-second domain it requires large amounts of micro crystals, specialized beamlines and considerable experience. Moreover, as the majority of enzymes displays turnover-times in the millisecond domain or slower, simpler methods can provide meaningful structural insight into enzyme catalysis. Vitrification of protein crystals can trap reaction intermediates by rapid cooling to ¡ 100 K, and has traditionally been used to gain insight into long lived reaction intermediates such as product complexes. However, manual vitrification procedures are limited to long delay times of at least several seconds and heavily suffer from operator variability. A solution to this problem is provided by automatic crystal plunging devices, such as the Spitrobot, that plunge loop-mounted protein crystals into liquid nitrogen within millisecond time-scales. Versatile means of reaction initiation can be achieved either by micro dispensing a ligand droplet, or via optical excitation of light-sensitive proteins, or via the photoactivation of caged compounds. In addition to the conceptual simplicity, another benefit of cryo-trapping is that data can be collected at conventional synchrotron beamlines, exploiting their robust high-throughput capabilities. Thus, compared to room-temperature time-resolved crystallography, users not only benefit from uncoupling sample-preparation and data-collection, but also from a reduction in the required technical expertise and ready access to radiation sources. However, as cryo-trapping crystallography explores dynamic structural changes that become only visible by the comparison of several samples, experiments have to be carefully planned to carry out the necessary controls and to avoid mis- or over-interpretation of the results. Here we describe a detailed protocol for cryo-trapping time-resolved crystallography using automated crystal-plungers that enables researchers to map enzymatic reaction coordinate pathways within the millisecond domain.

We previously introduced the spitrobot , a protein crystal plunging system that enables reaction quenching via cryo-trapping with a time resolution in the millisecond range. Here we present the next generation, spitrobot-2 , as an integrated benchtop device. User-friendliness has been improved by semi-automatic sample exchange. Moreover, a fully automated shutter shields the liquid nitrogen from the humidified environment, improving sample integrity. Most importantly, the cryo-trapping delay time has been reduced to 23 ms, making spitrobot-2 twice as fast as the previous generation. This further expands the number of target systems that can be addressed by cryo-trapping time-resolved crystallography. Using 12 crystal structures of three independent model systems, we demonstrate successful cryo-trapping via observation of conformational changes and ligand binding within 25 ms. These improvements increase the convenient access to cryo-trapping, time-resolved X-ray crystallography empowering the MX community with efficient tools to advance research in structural biology.

The vast majority of protein structures are determined at cryogenic temperatures, which are far from physiological conditions. Nevertheless, it is well established that temperature is an essential thermodynamic parameter for understanding the conformational dynamics and functionality of proteins in their native environments. Time-resolved crystallography is a technique that aims to elucidate protein function by examining structural alterations during processes such as ligand binding, catalysis, or allostery. However, this approach is typically conducted under ambient conditions, which may obscure crucial conformational states, that are only visible at physiological temperatures. In this study, we directly address the interplay between protein structure and activity via a method that enables multi-temperature, time-resolved serial crystallography experiments in a temperature window from below 10 °C to above 70 °C. Via this 5D-SSX, time-resolved experiments can now be carried out at physiological temperatures and with long time delays, providing insights into protein function and enzyme catalysis. Our findings demonstrate the temperature-dependent modulation of turnover kinetics for the mesophilic β-lactamase CTX-M-14 and the thermophilic enzyme xylose isomerase, within the full protein structure

Proton transfer is a fundamental process underlying chemical and biological phenomena, and its dynamics are significantly influenced by the surrounding environment. This paper studies the excited state intramolecular proton transfer (ESIPT) process, which is crucial to the photostability of hydroxyanthraquinone-based pigments through efficient energy dissipation, by investigating how crystalline packing influences photoinduced proton transfer dynamics in single crystals of dihydroxyanthraquinone (DHAQ) constitutional isomers. Comparing the proton transfer dynamics in crystalline and solution phases, we show substantial differences due to the crystalline environment, particularly in the 1,4- and 1,5-DHAQ isomers. These isomers show intermolecular hydrogen bonding within the crystal lattice, resulting in larger excitonic couplings, which significantly alters their reaction pathways compared to their behaviour in solution. We show that 1,8-DHAQ, which does not form intermolecular hydrogen bonds in the crystal, shows minimal changes in dynamics between the phases. In contrast, in the case of 1,4-DHAQ, intermolecular interactions within the molecular crystal phase open up an ESIPT relaxation channel, which is not observed in the solution phase. These findings highlight the critical role of crystal packing in modulating proton transfer dynamics and offer insights into how molecular packing can be strategically manipulated to control and optimize reaction pathways in solid-state environments.

We previously introduced the SPITROBOT, a protein crystal plunging system that enables reaction quenching via cryo-trapping with a time resolution in the millisecond range. Here we present the next generation, SPITROBOT-2, as an integrated benchtop device, condensed to approximately an A4 footprint. The user experience has been enhanced by the integration of a guiding beam and a sample-switch dial, to optimise sample exchange operations. This is complemented by a light-indicated liquid nitrogen level sensor, ensuring enhanced reliability. Moreover, a fully automated shutter shields the liquid nitrogen from the humidified environment, improving sample integrity. These improvements reduce the net sample preparation time to approximately three minutes per sample. Most importantly, the cryo-trapping delay time has been reduced to 23 milliseconds, making SPITROBOT-2 twice as fast as the previous generation. This further expands the number of target systems that can be addressed by cryo-trapping time-resolved crystallography. We demonstrate successful cryo-trapping via ligand binding and conformational changes using 12 crystal structures of three independent model systems: xylose isomerase, human insulin and bacteriophage T4 lysozyme. Taken together, these improvements increase the convenient access to cryo-trapping, time-resolved X-ray crystallography empowering the MX community with efficient tools to advance research in structural biology.

Recently, we introduced the liquid application method for time-resolved analyses (LAMA). The time-consuming cleaning cycles required for the substrate solution exchange and storage of the sensitive droplet-dispenser nozzles present practical challenges. In this work, a dispenser cleaning system for the semi-automated cleaning of the piezo-actuator-driven picolitre-droplet dispensers required for LAMA is introduced to streamline typical workflows.

We introduce the spitrobot, a protein crystal plunger, enabling reaction quenching via cryo-trapping with a time-resolution in the millisecond range. Protein crystals are mounted on canonical micromeshes on an electropneumatic piston, where the crystals are kept in a humidity and temperature-controlled environment, then reactions are initiated via the liquid application method (LAMA) and plunging into liquid nitrogen is initiated after an electronically set delay time to cryo-trap intermediate states. High-magnification images are automatically recorded before and after droplet deposition, prior to plunging. The SPINE-standard sample holder is directly plunged into a storage puck, enabling compatibility with high-throughput infrastructure. Here we demonstrate binding of glucose and 2,3-butanediol in microcrystals of xylose isomerase, and of avibactam and ampicillin in microcrystals of the extended spectrum beta-lactamase CTX-M-14. We also trap reaction intermediates and conformational changes in macroscopic crystals of tryptophan synthase to demonstrate that the spitrobot enables insight into catalytic events.

We introduce the spitrobot , a protein crystal plunger, enabling reaction quenching via cryo-trapping with millisecond time-resolution. Canonical micromesh loops are mounted on an electropneumatic piston, reactions are initiated via the liquid application method (LAMA), and finally intermediate states are cryo-trapped in liquid nitrogen. We demonstrate binding of several ligands in microcrystals of three enzymes, and trapping of reaction intermediates and conformational changes in macroscopic crystals of tryptophan synthase.

Thin single organic crystals (≤1 μm) with large area (≥100 × 100 μm²) are desirable to explore photoinduced processes using ultrafast spectroscopy and electron-diffraction. Here, we present a general method based on spatial confinement to grow such crystals using the prototypical proton transfer system, 1,5-dihydroxyanthraquinone, as an example, and provide the protocol for optically characterizing structural dynamics to enable proper assignments using diffraction methods.

We present an environmental enclosure for fixed-target serial crystallography, enabling X-ray diffraction experiments in a temperature window from below 10 °C to above 70 °C - a universal parameter of protein function. Via 5D-SSX time-resolved experiments can now be carried out at physiological temperatures, providing fundamentally new insights into protein function. We show temperature-dependent modulation of turnover kinetics for the mesophilic β -lactamase CTX-M-14 and for the hyperthermophilic enzyme xylose isomerase.