Membranes Are Decisive for Maximum Freezing Efficiency of Bacterial Ice Nucleators

Ice-nucleating proteins (INPs) from Pseudomonas syringae are among the most active ice nucleators known, enabling ice formation at temperatures close to the melting point of water. The working mechanisms of INPs remain elusive, but their ice nucleation activity has been proposed to depend on the ability to form large INP aggregates. Here, we provide experimental evidence that INPs alone are not sufficient to achieve maximum freezing efficiency and that intact membranes are critical. Ice nucleation measurements of phospholipids and lipopolysaccharides show that these membrane components are not part of the active nucleation site but rather enable INP assembly. Substantially improved ice nucleation by INP assemblies is observed for deuterated water, indicating stabilization of assemblies by the stronger hydrogen bonds of D2O. Together, these results show that the degree of order/disorder and the assembly size are critically important in determining the extent to which bacterial INPs can facilitate ice nucleation.We thank L. Reichelt, N. Bothen, and N. M. Kropf for technical assistance. The TOC graphic and Figures 1 and 2B were created using BioRender.com.Ye

Hollow glass microspheres as potential adjunct with orthopaedic metal implants

Glass particles both in nano and micro scale; have found applications in the medical field, like tissue engineering, controlled delivery vehicles for drugs, proteins, antibiotics, etc. They are used in the form of bioactive glass, polymeric bioactive glass scaffolds, and hollow/porous glass microspheres. The hollow glass microspheres are thin walled, porous glass microspheres 10-100 mu m or more in diameter. The unique properties of the microspheres which make them a potential candidate for bio-medical applications are their mechanical strength, biocompatible nature, small easily administrable size, high surface area, even distribution, light weight, specific buoyant density and controllable pores allowing selective uptake and release of bio molecules. There are a couple of well established HGMs preparation methods listed in literature, where rotating arc plasma and vertical tube furnace are used to spheroidize the raw material sprayed in powder or slurry form. In this research work, we have prepared HGMs from amber colored glass frits by flame spheroidization method. Prepared HGMs were then soaked in Simulated Body Fluid (SBF) for in vitro bioactivity determination. HGMs were soaked for 1-2 weeks and bioactivity was confirmed by the development of hydroxyapatite (HA) layer over the surface of HGMs. The HA formation was confirmed by the crystalline peak of HA obtained in X-ray diffraction spectra owing to the presence of crystalline calcium phosphate layer of HA, Ca-10(PO4)(6)(OH)(2) as well as by determining weight percentage of corresponding elements by EDS Spectra. In vitro bioactivity of HGMs thus makes them biocompatible and renders them for use in orthopaedics field. They can contribute effectively when used in conjunction with metallic implants in order to enhance its mechanical strength as well as biocompatibility. (C) 2014 Elsevier B.V. All rights reserved

Optimizing pump-probe reflectivity measurements of ultrafast photoacoustics with modulated asynchronous optical sampling

Time-resolved optical pump-probe experiments enable the study of complex light-matter interactions on ultrafast timescales, provided that they reach sufficient sensitivity. For instance, with pump-induced ultrafast photoacoustics, probing the typically small changes in optical properties requires a high signal-to-noise ratio. Asynchronous optical sampling (ASOPS), using two separate pulsed lasers at slightly different repetition rates, can be effective at removing noise by averaging many rapidly acquired traces. However, the pump-probe delay scan with ASOPS is always as long as the pump pulse interval, which is inefficient if the delay-time range of interest is shorter. Here, we demonstrate two modified ASOPS schemes that optimize measurement efficiency by only scanning the range of interest. The modification based on frequency modulated ASOPS (MASOPS) is most efficient, especially in the presence of low-frequency flicker noise. We provide a proof-of-concept measurement of ultrafast photoacoustics in which we use MASOPS to scan a time delay of 1/20 of the pump pulse interval. The resulting noise floor is 20 times lower compared to conventional ASOPS, allowing for 20 times faster measurements. Furthermore, we show that by taking experimental noise characteristics into account, more traditional pump-probe methods can also be optimized.</p