Yong-Ming Liu

Evaporation rate of water as a function of a magnetic field and field gradient.

The effect of magnetic fields on water is still a highly controversial topic despite the vast amount of research devoted to this topic in past decades. Enhanced water evaporation in a magnetic field, however, is less disputed. The underlying mechanism for this phenomenon has been investigated in previous studies. In this paper, we present an investigation of the evaporation of water in a large gradient magnetic field. The evaporation of pure water at simulated gravity positions (0 gravity level (ab. g), 1 g, 1.56 g and 1.96 g) in a superconducting magnet was compared with that in the absence of the magnetic field. The results showed that the evaporation of water was indeed faster in the magnetic field than in the absence of the magnetic field. Furthermore, the amount of water evaporation differed depending on the position of the sample within the magnetic field. In particular, the evaporation at 0 g was clearly faster than that at other positions. The results are discussed from the point of view of the evaporation surface area of the water/air interface and the convection induced by the magnetization force due to the difference in the magnetic susceptibility of water vapor and the surrounding air.

Effect of mechanical vibration on protein crystallization

Mechanical vibration often occurs during protein crystallization; however, it is seldom considered as one of the factors influencing the crystallization process. This paper reports an investigation of the crystallization of five proteins using various crystallization conditions in a temperature-controlled chamber on the table of a mechanical vibrator. The results show that mechanical vibration can reduce the number of crystals and improve their optical perfection. During screening of the crystallization conditions it was found that mechanical vibration could help to obtain crystals in a highly supersaturated solution in which amorphous precipitates often normally appear. It is concluded that mechanical vibration can serve as a tool for growing optically perfect crystals or for obtaining more crystallization conditions during crystallization screening.

Utilisation of adsorption and desorption for simultaneously improving protein crystallisation success rate and crystal quality

High-quality protein crystals of suitable size are an important prerequisite for applying X-ray crystallography to determine the 3-dimensional structure of proteins. However, it is often difficult to obtain protein crystals of appropriate size and quality because nucleation and growth processes can be unsuccessful. Here, we show that by adsorbing proteins onto porous polystyrene-divinylbenzene microspheres (SDB) floating on the surface of the crystallisation solution, a localised high supersaturation region at the surface of the microspheres and a low supersaturation region below the microspheres can coexist in a single solution. The crystals will easily nucleate in the region of high supersaturation, but when they grow to a certain size, they will sediment to the region of low supersaturation and continue to grow. In this way, the probability of crystallisation and crystal quality can be simultaneously increased in a single solution without changing other crystallisation parameters.

An ignored variable: solution preparation temperature in protein crystallization

Protein crystallization is affected by many parameters, among which certain parameters have not been well controlled. The temperature at which the protein and precipitant solutions are mixed (i.e., the ambient temperature during mixing) is such a parameter that is typically not well controlled and is often ignored. In this paper, we show that this temperature can influence protein crystallization. The experimental results showed that both higher and lower mixing temperatures can enhance the success of crystallization, which follows a parabolic curve with an increasing ambient temperature. This work illustrates that the crystallization solution preparation temperature is also an important parameter for protein crystallization. Uncontrolled or poorly controlled room temperature may yield poor reproducibility in protein crystallization.

Replacing a reservoir solution with desiccant in vapor diffusion protein crystallization screening

This paper presents a modification to the conventional vapor diffusion (hanging- or sitting-drop) technique for protein crystallization screening. In this modified method, the reservoir solution is replaced with a desiccant to allow for a larger range of protein solution concentrations, thereby providing more opportunities for crystal formation. This method was tested in both reproducibility and screening studies, and the results showed that it significantly improves the efficiency and reduces the cost of protein crystallization screens.

Promoting protein crystallization using a plate with simple geometry

Increasing the probability of obtaining protein crystals in crystallization screening is always an important goal for protein crystallography. In this paper, a new method called the cross-diffusion microbatch (CDM) method is presented, which aims to efficiently promote protein crystallization and increase the chance of obtaining protein crystals. In this method, a very simple crystallization plate was designed in which all crystallization droplets are in one sealed space, so that a variety of volatile components from one droplet can diffuse into any other droplet via vapour diffusion. Crystallization screening and reproducibility tests indicate that this method could be a potentially powerful technique in practical protein crystallization screening. It can help to obtain crystals with higher probability and at a lower cost, while using a simple and easy procedure.

An Investigation of the Effects of Self-Assembled Monolayers on Protein Crystallisation

Most protein crystallisation begins from heterogeneous nucleation; in practice, crystallisation typically occurs in the presence of a solid surface in the solution. The solid surface provides a nucleation site such that the energy barrier for nucleation is lower on the surface than in the bulk solution. Different types of solid surfaces exhibit different surface energies, and the nucleation barriers depend on the characteristics of the solid surfaces. Therefore, treatment of the solid surface may alter the surface properties to increase the chance to obtain protein crystals. In this paper, we propose a method to modify the glass cover slip using a self-assembled monolayer (SAM) of functional groups (methyl, sulfydryl and amino), and we investigated the effect of each SAM on protein crystallisation. The results indicated that both crystallisation success rate in a reproducibility study, and crystallisation hits in a crystallisation screening study, were increased using the SAMs, among which, the methyl-modified SAM demonstrated the most significant improvement. These results illustrated that directly modifying the crystallisation plates or glass cover slips to create surfaces that favour heterogeneous nucleation can be potentially useful in practical protein crystallisation, and the utilisation of a SAM containing a functional group can be considered a promising technique for the treatment of the surfaces that will directly contact the crystallisation solution.

A new method to realize high-throughput protein crystallization in a superconducting magnet

We present a new method for the realization of high-throughput protein crystallization screening using an array of 96 capillaries aligned in a circle. In this method, each capillary represents a single crystallization condition, and all capillaries experience identical magnetic field conditions. After crystallization, the crystals in the capillary can be directly diffracted without harvesting. This method proved easy to perform and is applicable for use in magnetic fields and may be further extended for use in other circumstances, for example, under space microgravity conditions.

Surface treatment by oxidizing the plates can alter the response of protein crystallization

This report describes the modification of crystallization plates by simply oxidizing the surface of the protein wells. The oxidized crystallization plates were tested in standard protein crystallization screening and reproducibility studies. The results showed that the protein wells of the treated plates were smoother and more optically transparent than those of the untreated plates, and more importantly, protein crystallization was significantly promoted after the oxidation treatment. Because there is no change to the routine screening protocol, this method is simple and easy to apply in protein crystallization.

Selecting temperature for protein crystallization screens using the temperature dependence of the second virial coefficient.

Protein crystals usually grow at a preferable temperature which is however not known for a new protein. This paper reports a new approach for determination of favorable crystallization temperature, which can be adopted to facilitate the crystallization screening process. By taking advantage of the correlation between the temperature dependence of the second virial coefficient (B 22) and the solubility of protein, we measured the temperature dependence of B 22 to predict the temperature dependence of the solubility. Using information about solubility versus temperature, a preferred crystallization temperature can be proposed. If B 22 is a positive function of the temperature, a lower crystallization temperature is recommended; if B 22 shows opposite behavior with respect to the temperature, a higher crystallization temperature is preferred. Otherwise, any temperature in the tested range can be used.