Ultrasonic acoustic levitation for fast frame rate X-ray protein crystallography at room temperature

Contactless ultrasound droplet manipulation system for mixing chemical reagents

Green chemistry has been a rising topic in environmental sustainability, with a focus on the waste and consumption reduction of chemical and biomedical industries. Traditional chemical handling processes require tools that contact chemical reagents to produce vast amounts of residues and disposals. This study presents a contactless chemical mixing system that integrates acoustic droplet ejection and levitation techniques. First, the acoustic droplet ejection system creates a droplet in mid-air from a designated liquid reservoir by focusing acoustic energy at the liquid-air junction. The droplet levitation system captures and transports the droplet along a predetermined path by shifting the focal points of the acoustic standing waves. This facilitates contactless mixing of chemicals in a defined ratio. Notably, this study employs piezoelectric discs in an acoustic droplet ejection system to eject droplets from liquids. The relationship between the duration of the driving bursts and height and size of ejected droplets was also investigated. The proposed acoustic standing wave levitation system captures droplets with weights between 2.8 and 5.2 mg. To assess the reliability of the proposed system, 25 droplets were sequentially generated and transported to the mixing well without failure. The root mean square error between the collected and expected liquid weights was only 0.098 mg. The proposed system offers a promising solution for reducing waste and promoting environmentally friendly practices in chemical and biomedical laboratories.

Bridging the microscopic divide: a comprehensive overview of micro-crystallization and in vivo crystallography

A series of events underscoring the significant advancements in micro-crystallization and in vivo crystallography were held during the 26th IUCr Congress in Melbourne, positioning microcrystallography as a pivotal field within structural biology. Through collaborative discussions and the sharing of innovative methodologies, these sessions outlined frontier approaches in macromolecular crystallography. This review provides an overview of this rapidly moving field in light of the rich dialogues and forward-thinking proposals explored during the congress workshop and microsymposium. These advances in microcrystallography shed light on the potential to reshape current research paradigms and enhance our comprehension of biological mechanisms at the molecular scale.

On the dynamics of a big drop in acoustic levitation

The acoustic levitation of a drop is a complex process that needs a high-intensity non-linear acoustic field; the sound pressure level has to be sufficient to raise the drop but not too large to avoid its atomization, limiting the maximum size of a levitated drop. In this paper, we present an experimental study of big drops levitation with a volume up to 166±2μl and with an effective diameter 6.82±0.03mm, figures one magnitude order larger than the maximum drop volume reported in the literature. Our acoustic levitator produces an acoustic field with a different shape than the field produced by a typical levitator. Our measurements and simulations of the acoustic field and drop dynamics suggest that the levitation of big drops is possible because the distribution of radiation pressure over the drop surface in our system differs from that in a typical acoustic levitator; its maximum value appears on the top surface of the drop and not in its equator. In addition, we determined the upper and lower limits of sound pressure necessary for the levitation of drops of various sizes that allow our system.

Hydrodynamic coupling melts acoustically levitated crystalline rafts

Going beyond the manipulation of individual particles, first steps have recently been undertaken with acoustic levitation in air to investigate the collective dynamical properties of many-body systems self-assembled within the levitation plane. However, these assemblies have been limited to two-dimensional, close-packed rafts where forces due to scattered sound pull particles into direct frictional contact. Here, we overcome this restriction using particles small enough that the viscosity of air establishes a repulsive streaming flow at close range. By tuning the particle size relative to the characteristic length scale for viscous streaming, we control the interplay between attractive and repulsive forces and show how particles can be assembled into monolayer lattices with tunable spacing. While the strength of the levitating sound field does not affect the particles' steady-state separation, it controls the emergence of spontaneous excitations that can drive particle rearrangements in an effectively dissipationless, underdamped environment. Under the action of these excitations, a quiescent particle lattice transitions from a predominantly crystalline structure to a two-dimensional liquid-like state. We find that this transition is characterized by dynamic heterogeneity and intermittency, involving cooperative particle movements that remove the timescale associated with caging for the crystalline lattice. These results shed light on the nature of athermal excitations and instabilities that can arise from strong hydrodynamic coupling among interacting particles.

Airborne ultrasound pulse amplification based on acoustic resonance switching

Airborne ultrasound radiation pressure, a nonlinear effect that appears as a static force in mid-air in the presence of strong ultrasound, has recently been applied in novel scientific and industrial fields. However, the output power of an ultrasound transducer remains low mainly due to the significant mismatch in acoustic impedance between a solid diaphragm and air. To circumvent this fundamental challenge, we propose to emit amplified airborne ultrasound pulses by instantaneously releasing stored acoustic energy into free-space. Specifically, we implement an acoustic cavity with a mechanically rotating shutter covering its open top. Once the acoustic cavity is fully charged, the stored energy is released by opening the shutter. By developing a choke structure that reduces leakage of the stored energy, we generate ultrasound pulses with 2.5 times higher peak power than the input continuous waves at 40 kHz. This preliminary result has a great potential to generate high-power ultrasound pulses using a conventional air-coupled transducer by separating the storage and radiation process, thus circumventing the fundamental limitation brought by impedance mismatch.

Acoustic levitation and rotation of thin films and their application for room temperature protein crystallography

Acoustic levitation has attracted attention in terms of chemical and biochemical analysis in combination with various analytical methods because of its unique container-less environment for samples that is not reliant on specific material characteristics. However, loading samples with very high viscosity is difficult. To expand the scope, we propose the use of polymer thin films as sample holders, whereby the sample is dispensed on a film that is subsequently loaded onto an acoustic levitator. When applied for protein crystallography experiments, rotation controllability and positional stability are important prerequisites. We therefore study the acoustic levitation and rotation of thin films with an aspect ratio (the diameter-to-thickness ratio) of 80-240, which is an order of magnitude larger than those reported previously. For films with empirically optimized shapes, we find that it is possible to control the rotation speed in the range of 1-4 rotations per second while maintaining a positional stability of 12 ± 5 µm. The acoustic radiation force acting on the films is found to be a factor of 26-30 higher than that for same-volume water droplets. We propose use cases of the developed films for protein crystallography experiments and demonstrate data collections for large single crystal samples at room temperature.

Measurement of Secondary Structure Changes in Poly-L-lysine and Lysozyme during Acoustically Levitated Single Droplet Drying Experiments by In Situ Raman Spectroscopy

Drying processes such as spray drying, as commonly used in the pharmaceutical industry to convert protein-based drugs into their particulate form, can lead to an irreversible loss of protein activity caused by protein secondary structure changes. Due to the nature of these processes (high droplet number, short drying time), an in situ investigation of the structural changes occurring during a real drying process is hardly possible. Therefore, an approach for the in situ investigation of the expected secondary structural changes during single droplet protein drying in an acoustic levitator by time-resolved Raman spectroscopy was developed and is demonstrated in this paper. For that purpose, a self-developed NIR–Raman sensor generates and detects the Raman signal from the levitated solution droplet. A mathematical spectral reconstruction by multiple Voigt functions is used to quantify the relative secondary structure changes occurring during the drying process. With the developed setup, it was possible to detect and quantify the relative secondary structure changes occurring during single droplet drying experiments for the two chosen model substances: poly-L-lysine, a homopolypeptide widely used as a protein mimic, and lysozyme. Throughout drying, an increase in the β-sheet structure and a decrease in the other two structural elements, α-helix, and random coil, could be identified. In addition, it was observed that the degree of structural changes increased with increasing temperature.

Dynamic Acoustic Levitator Based On Subwavelength Aperture Control

Acoustic levitation provides a means to achieve contactless manipulation of fragile materials and biological samples. Most acoustic levitators rely on complex electronic hardware and software to shape the acoustic field and realize their dynamic operation. Here, the authors introduce a dynamic acoustic levitator that is based on mechanically controlling the opening and (partial) closing of subwavelength apertures. This simple approach relies on the use of a single ultrasonic transducer and is shown to permit the facile and reliable manipulation of a variety targets ranging from solid particles, to fluid and ferrofluidic drops. Experimental observations agree well with numerical simulations of the Gor'kov potential. Remarkably, this system even enables the generation of time-varying potentials and induces oscillatory and rotational motion in the levitated objects via a feedback mechanism between the trapped object and the trapping potential. This is shown to result in long distance translation, in-situ rotation and self-modulated oscillation of the trapped particles. In addition, dense ferrofluidic droplets are levitated and transformed inside the levitator. Controlling subwavelength apertures opens the possibility to realize simple powerful levitators that nevertheless allow for the versatile dynamic manipulation of levitated matter.

Macromolecular room temperature crystallography

X-ray crystallography enables detailed structural studies of proteins to understand and modulate their function. Conducting crystallographic experiments at cryogenic temperatures has practical benefits but potentially limits the identification of functionally important alternative protein conformations that can be revealed only at room temperature (RT). This review discusses practical aspects of preparing, acquiring, and analyzing X-ray crystallography data at RT to demystify preconceived impracticalities that freeze progress of routine RT data collection at synchrotron sources. Examples are presented as conceptual and experimental templates to enable the design of RT-inspired studies; they illustrate the diversity and utility of gaining novel insights into protein conformational landscapes. An integrative view of protein conformational dynamics enables opportunities to advance basic and biomedical research.

Serial Crystallography for Structure-Based Drug Discovery

Rational drug discovery has greatly accelerated the development of safer and more efficacious therapeutics, assisted significantly by insights from experimentally determined 3D structures of ligands in complex with their targets. Serial crystallography (SX) with X-ray free-electron lasers has enabled structural determination using micrometer- or nanometer-size crystals. This technology, applied in the past decade to solve structures of notoriously difficult-to-study drug targets at room temperature, has now been adapted for use in synchrotron radiation facilities. Ultrashort time scales allow time-resolved characterization of dynamic structural changes and pave the road to study the molecular mechanisms by 'molecular movie.' This article summarizes the latest progress in SX technology and deliberates its demanding applications in future structure-based drug discovery.

Current status and future opportunities for serial crystallography at MAX IV Laboratory

Over the last decade, serial crystallography, a method to collect complete diffraction datasets from a large number of microcrystals delivered and exposed to an X-ray beam in random orientations at room temperature, has been successfully implemented at X-ray free-electron lasers and synchrotron radiation facility beamlines. This development relies on a growing variety of sample presentation methods, including different fixed target supports, injection methods using gas-dynamic virtual-nozzle injectors and high-viscosity extrusion injectors, and acoustic levitation of droplets, each with unique requirements. In comparison with X-ray free-electron lasers, increased beam time availability makes synchrotron facilities very attractive to perform serial synchrotron X-ray crystallography (SSX) experiments. Within this work, the possibilities to perform SSX at BioMAX, the first macromolecular crystallography beamline at  MAX IV Laboratory in Lund, Sweden, are described, together with case studies from the SSX user program: an implementation of a high-viscosity extrusion injector to perform room temperature serial crystallography at BioMAX using two solid supports - silicon nitride membranes (Silson, UK) and XtalTool (Jena Bioscience, Germany). Future perspectives for the dedicated serial crystallography beamline MicroMAX at MAX IV Laboratory, which will provide parallel and intense micrometre-sized X-ray beams, are discussed.

Coalescence Dynamics of Acoustically Levitated Droplets

The contactless coalescence of a droplet is of paramount importance for physical and industrial applications. This paper describes a coalescence method to be used mid-air via acoustic levitation using an ultrasonic phased array system. Acoustic levitation using ultrasonic phased arrays provides promising lab-on-a-drop applications, such as transportation, coalescence, mixing, separation, evaporation, and extraction in a continuous operation. The mechanism of droplet coalescence in mid-air may be better understood by experimentally and numerically exploring the droplet dynamics immediately before the coalescence. In this study, water droplets were experimentally levitated, transported, and coalesced by controlled acoustic fields. We observed that the edges of droplets deformed and attracted each other immediately before the coalescence. Through image processing, the radii of curvature of the droplets were quantified and the pressure difference between the inside and outside a droplet was simulated to obtain the pressure and velocity information on the droplet's surface. The results revealed that the sound pressure acting on the droplet clearly decreased before the impact of the droplets. This pressure on the droplets was quantitatively analyzed from the experimental data. Our experimental and numerical results provide deeper physical insights into contactless droplet manipulation for futuristic lab-on-a-drop applications.

Towards an Optimal Sample Delivery Method for Serial Crystallography at XFEL

The advent of the X-ray free electron laser (XFEL) in the last decade created the discipline of serial crystallography but also the challenge of how crystal samples are delivered to X-ray. Early sample delivery methods demonstrated the proof-of-concept for serial crystallography and XFEL but were beset with challenges of high sample consumption, jet clogging and low data collection efficiency. The potential of XFEL and serial crystallography as the next frontier of structural solution by X-ray for small and weakly diffracting crystals and provision of ultra-fast time-resolved structural data spawned a huge amount of scientific interest and innovation. To utilize the full potential of XFEL and broaden its applicability to a larger variety of biological samples, researchers are challenged to develop better sample delivery methods. Thus, sample delivery is one of the key areas of research and development in the serial crystallography scientific community. Sample delivery currently falls into three main systems: jet-based methods, fixed-target chips, and drop-on-demand. Huge strides have since been made in reducing sample consumption and improving data collection efficiency, thus enabling the use of XFEL for many biological systems to provide high-resolution, radiation damage-free structural data as well as time-resolved dynamics studies. This review summarizes the current main strategies in sample delivery and their respective pros and cons, as well as some future direction.

Acoustic levitation with optimized reflective metamaterials

The simplest and most commonly used acoustic levitator is comprised of a transmitter and an opposing reflecting surface. This type of device, however, is only able to levitate objects along one direction, at distances multiple of half of a wavelength. In this work, we show how a customised reflective acoustic metamaterial enables the levitation of multiple particles, not necessarily on a line and with arbitrary mutual distances, starting with a generic input wave. We establish a heuristic optimisation technique for the design of the metamaterial, where the local height of the surface is used to introduce delay patterns to the reflected signals. Our method stands for any type and number of sources, spatial resolution of the metamaterial and system's variables (i.e. source position, phase and amplitude, metamaterial's geometry, relative position of the levitation points, etc.). Finally, we explore how the strength of multiple levitation points changes with their relative distance, demonstrating sub-wavelength field control over levitating polystyrene beads into various configurations.

Concentrated protein solutions investigated using acoustic levitation and small-angle X-ray scattering

An acoustically levitated droplet has been used to collect synchrotron SAXS data on human serum albumin protein solutions up to a protein concentration of 400 mg ml^-1. A careful selection of experiments allows for fast data collection of a large amount of data, spanning a protein concentration/solvent concentration space with limited sample consumption (down to 3 µL per experiment) and few measurements. The data analysis shows data of high quality that are reproducible and comparable with data from standard flow-through capillary-based experiments. Furthermore, using this methodology, it is possible to achieve concentrations that would not be accessible by conventional cells. The protein concentration and ionic strength parameter space diagram may be covered easily and the amount of protein sample is significantly reduced (by a factor of 100 in this work). Used in routine measurements, the benefits in terms of protein cost and time spent are very significant.

Evaporation and drying kinetics of water-NaCl droplets via acoustic levitation

The acoustic levitation method (ALM) is expected to be applied as a container-less processing technology in the material science, analytical chemistry, biomedical technology, and food science domains because this method can be used to levitate any sample in mid-air and prevent nucleation and contamination due to the container wall. However, this approach can lead to nonlinear behavior, such as acoustic streaming, which promotes the evaporation of a levitated droplet. This study aims to understand the evaporation and precipitation kinetics of an acoustically levitated multicomponent droplet. An experimental investigation of the evaporation process of a salt solution droplet was performed, and the experimental results were compared with those of the d ²-law. The droplet was noted to evaporate in two stages owing to the precipitation of the salt. Because of the vapor pressure depression, the experimental data did not agree with the classical prediction obtained using the d ²-law. However, the experimental results were in partial agreement with those of the d ²-law when the vapor pressure depression was considered by using the concentration estimate at each time, as obtained from the experimental results. In addition, it was observed that the time when the salt completely precipitated could be estimated by using the extended theory. These findings provide physical and practical insights into the droplet evaporation mid-air for potential lab-in-a-drop applications.

Acoustic Manipulation of Droplets under Reduced Gravity

Contactless manipulation of matter is essential for studying physical phenomena. Acoustic manipulation of liquid samples using ultrasonic phased arrays provides a novel and attractive solution for mid-air manipulation, such as levitation, transportation, coalescence, mixing, separation, evaporation, and extraction, with a simple and single sequence. Despite the importance of gravity in droplet dynamics, its effect on a levitated droplet with an ultrasonic phased array remains unclear. To disseminate acoustic manipulation, better understanding of the fundamental physics of a droplet manipulated by ultrasonic phased arrays is required. Here, we show contactless levitation, transportation, and coalescence of multiple droplets under both ground and reduced gravity. Under ground gravity, the possible levitation size of the sample is limited to below the half wavelength of sound. Under reduced gravity, however, droplets that are larger than the limit can be successfully levitated, transported, and coalesced. Furthermore, the threshold of sound pressure for droplet levitation and manipulation could be minimised with the suppression of nonlinear acoustic phenomena under reduced gravity. These insights promote the development of contactless manipulation techniques of droplets for future space experiment and inhabitancy.

Non-Contact Universal Sample Presentation for Room Temperature Macromolecular Crystallography Using Acoustic Levitation

Macromolecular Crystallography is a powerful and valuable technique to assess protein structures. Samples are commonly cryogenically cooled to minimise radiation damage effects from the X-ray beam, but low temperatures hinder normal protein functions and this procedure can introduce structural artefacts. Previous experiments utilising acoustic levitation for beamline science have focused on Langevin horns which deliver significant power to the confined droplet and are complex to set up accurately. In this work, the low power, portable TinyLev acoustic levitation system is used in combination with an approach to dispense and contain droplets, free of physical sample support to aid protein crystallography experiments. This method facilitates efficient X-ray data acquisition in ambient conditions compatible with dynamic studies. Levitated samples remain free of interference from fixed sample mounts, receive negligible heating, do not suffer significant evaporation and since the system occupies a small volume, can be readily installed at other light sources.

Two-Dimensional Manipulation in Mid-Air Using a Single Transducer Acoustic Levitator

We report a single transducer acoustic levitator capable of manipulating objects in two-dimensions. The levitator consists of a centrally actuated vibrating plate and a flat reflector. We show that the levitation position of the object depends not only on the vibration frequency, but also on the tilting angle between the plate and the reflector. Additionally, new levitation positions can be created by actuating the plate with a composite signal of two frequencies using frequency switching. Based on recorded levitation positions, such single transducer acoustic levitator can manipulate a cluster of levitated microspheres in predefined trajectories, with mean position error of 155 ± 84 µm.

Strategies for sample delivery for femtosecond crystallography

Highly efficient data-collection methods are required for successful macromolecular crystallography (MX) experiments at X-ray free-electron lasers (XFELs). XFEL beamtime is scarce, and the high peak brightness of each XFEL pulse destroys the exposed crystal volume. It is therefore necessary to combine diffraction images from a large number of crystals (hundreds to hundreds of thousands) to obtain a final data set, bringing about sample-refreshment challenges that have previously been unknown to the MX synchrotron community. In view of this experimental complexity, a number of sample delivery methods have emerged, each with specific requirements, drawbacks and advantages. To provide useful selection criteria for future experiments, this review summarizes the currently available sample delivery methods, emphasising the basic principles and the specific sample requirements. Two main approaches to sample delivery are first covered: (i) injector methods with liquid or viscous media and (ii) fixed-target methods using large crystals or using microcrystals inside multi-crystal holders or chips. Additionally, hybrid methods such as acoustic droplet ejection and crystal extraction are covered, which combine the advantages of both fixed-target and injector approaches.

Acoustic tweezers for the life sciences

Acoustic tweezers are a versatile set of tools that use sound waves to manipulate bioparticles ranging from nanometer-sized extracellular vesicles to millimeter-sized multicellular organisms. Over the past several decades, the capabilities of acoustic tweezers have expanded from simplistic particle trapping to precise rotation and translation of cells and organisms in three dimensions. Recent advances have led to reconfigured acoustic tweezers that are capable of separating, enriching, and patterning bioparticles in complex solutions. Here, we review the history and fundamentals of acoustic-tweezer technology and summarize recent breakthroughs.

Using sound pulses to solve the crystal-harvesting bottleneck

Crystal harvesting has proven to be difficult to automate and remains the rate-limiting step for many structure-determination and high-throughput screening projects. This has resulted in crystals being prepared more rapidly than they can be harvested for X-ray data collection. Fourth-generation synchrotrons will support extraordinarily rapid rates of data acquisition, putting further pressure on the crystal-harvesting bottleneck. Here, a simple solution is reported in which crystals can be acoustically harvested from slightly modified MiTeGen In Situ-1 crystallization plates. This technique uses an acoustic pulse to eject each crystal out of its crystallization well, through a short air column and onto a micro-mesh (improving on previous work, which required separately grown crystals to be transferred before harvesting). Crystals can be individually harvested or can be serially combined with a chemical library such as a fragment library.

Contactless Fluid Manipulation in Air: Droplet Coalescence and Active Mixing by Acoustic Levitation

Acoustic manipulation by an ultrasonic phased array provides an entirely new approach to processes such as coalescence, mixing, separation, and evaporation occurring in the generation of new materials, physical property measurement, the biomedical industry, etc. However, to date, ultrasonic phased arrays have not been fully investigated for applications in fluid manipulation. This paper provides contactless coalescence and mixing techniques for droplets in air by controlling the acoustic potential by using an ultrasonic phased array. We focused on mode oscillation to propose an efficient mixing technique for liquid without contact. A comparison of mixing performance between cases with mode oscillation and without mode oscillation showed that the flow induced by mode oscillation promotes droplet mixing. Our paper demonstrates the feasibility of contactless coalescence and mixing as a first step in fluid manipulation with a phased array.

An acoustic on-chip goniometer for room temperature macromolecular crystallography

This paper describes the design, development and successful use of an on-chip goniometer for room-temperature macromolecular crystallography via acoustically induced rotations. We present for the first time a low cost, rate-tunable, acoustic actuator for gradual in-fluid sample reorientation about varying axes and its utilisation for protein structure determination on a synchrotron beamline. The device enables the efficient collection of diffraction data via a rotation method from a sample within a surface confined droplet. This method facilitates efficient macromolecular structural data acquisition in fluid environments for dynamical studies.

X-ray free electron laser: opportunities for drug discovery

Past decades have shown the impact of structural information derived from complexes of drug candidates with their protein targets to facilitate the discovery of safe and effective medicines. Despite recent developments in single particle cryo-electron microscopy, X-ray crystallography has been the main method to derive structural information. The unique properties of X-ray free electron laser (XFEL) with unmet peak brilliance and beam focus allow X-ray diffraction data recording and successful structure determination from smaller and weaker diffracting crystals shortening timelines in crystal optimization. To further capitalize on the XFEL advantage, innovations in crystal sample delivery for the X-ray experiment, data collection and processing methods are required. This development was a key contributor to serial crystallography allowing structure determination at room temperature yielding physiologically more relevant structures. Adding the time resolution provided by the femtosecond X-ray pulse will enable monitoring and capturing of dynamic processes of ligand binding and associated conformational changes with great impact to the design of candidate drug compounds.

Solution electrostatic levitator for measuring surface properties and bulk structures of an extremely supersaturated solution drop above metastable zone width limit

We report on the first integrated apparatus for measuring surface and thermophysical properties and bulk structures of a highly supersaturated solution by combining electrostatic levitation with real-time laser/x-ray scattering. Even today, a proper characterization of supersaturated solutions far above their solubility limits is extremely challenging because heterogeneous nucleation sites such as container walls or impurities readily initiate crystallization before the measurements can be performed. In this work, we demonstrate simultaneous measurements of drying kinetics and surface tension of a potassium dihydrogen phosphate (KH₂PO₄) aqueous solution droplet and its bulk structural evolution beyond the metastable zone width limit. Our experimental finding shows that the noticeable changes of the surface properties are accompanied by polymerizations of hydrated monomer clusters. The novel electrostatic levitation apparatus presented here provides an effective means for studying a wide range of highly concentrated solutions and liquids in deep metastable states.

Huygens-Fresnel Acoustic Interference and the Development of Robust Time-Averaged Patterns from Traveling Surface Acoustic Waves

Periodic pattern generation using time-averaged acoustic forces conventionally requires the intersection of counterpropagating wave fields, where suspended micro-objects in a microfluidic system collect along force potential minimizing nodal or antinodal lines. Whereas this effect typically requires either multiple transducer elements or whole channel resonance, we report the generation of scalable periodic patterning positions without either of these conditions. A single propagating surface acoustic wave interacts with the proximal channel wall to produce a knife-edge effect according to the Huygens-Fresnel principle, where these cylindrically propagating waves interfere with classical wave fronts emanating from the substrate. We simulate these conditions and describe a model that accurately predicts the lateral spacing of these positions in a robust and novel approach to acoustic patterning.

Serial Synchrotron X-Ray Crystallography (SSX)

Prompted by methodological advances in measurements with X-ray free electron lasers, it was realized in the last two years that traditional (or conventional) methods for data collection from crystals of macromolecular specimens can be complemented by synchrotron measurements on microcrystals that would individually not suffice for a complete data set. Measuring, processing, and merging many partial data sets of this kind requires new techniques which have since been implemented at several third-generation synchrotron facilities, and are described here. Among these, we particularly focus on the possibility of in situ measurements combined with in meso crystal preparations and data analysis with the XDS package and auxiliary programs.

EIGER detector: application in macromolecular crystallography

The development of single-photon-counting detectors, such as the PILATUS, has been a major recent breakthrough in macromolecular crystallography, enabling noise-free detection and novel data-acquisition modes. The new EIGER detector features a pixel size of 75 × 75 µm, frame rates of up to 3000 Hz and a dead time as low as 3.8 µs. An EIGER 1M and EIGER 16M were tested on Swiss Light Source beamlines X10SA and X06SA for their application in macromolecular crystallography. The combination of fast frame rates and a very short dead time allows high-quality data acquisition in a shorter time. The ultrafine ϕ-slicing data-collection method is introduced and validated and its application in finding the optimal rotation angle, a suitable rotation speed and a sufficient X-ray dose are presented. An improvement of the data quality up to slicing at one tenth of the mosaicity has been observed, which is much finer than expected based on previous findings. The influence of key data-collection parameters on data quality is discussed.