Lipid vesicles have been used as model cell systems, in which an in-vitro transcription-translation system (IVTT) is encapsulated to carry out intravesicular protein synthesis. Despite a large number of previous studies, a quantitative understanding of how protein synthesis inside the vesicles is affected by the lipid membrane remains elusive. This is mainly because of the heterogeneity in structural properties of the lipid vesicles used in the experiments. We investigated the effects of the phospholipid membrane on green fluorescent protein (GFP) synthesis occurring inside cell-sized giant unilamellar vesicles (GUV), which have a defined quantity of lipids relative to the reaction volume. We first developed a method to distinguish GUV from multilamellar vesicles using flow cytometry (FCM). Using this method, we investigated the time course of GFP synthesis using one of the IVTT, the PURE system, and found that phospholipid in the form of GUV has little effect on GFP synthesis based on three lines of investigation. (1) GFP synthesis inside the GUV was not dependent on the size of GUV (2) or on the fraction of cholesterol or anionic phospholipid constituting the GUV, and (3) GFP synthesis proceeded similarly in GUV and in the test tube. The present results suggest that GUV provides an ideal reaction environment that does not affect the internal biochemical reaction. On the other hand, we also found that internal GFP synthesis is strongly dependent on the chemical composition of the outer solution.

The permeability of giant unilamellar vesicle (GUV) membranes to various solutes was investigated at the single-vesicle level. Membrane permeability has primarily been studied by obtaining the average of vesicle ensembles using small or large unilamellar vesicles (SUVs and LUVs, respectively) <1 mm in diameter. The average properties observed for biological molecules or systems may not necessarily represent those of individual vesicles. In addition, although the GUV (>1 mm) is considered to be a primitive cell model, its membrane permeability has rarely been investigated. We investigated the permeation of various molecules, including amino acids and mononucleotides, through more than 20 000 GUV membranes composed of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) using flow cytometry. We observed a general trend of lower membrane permeability for polar or charged molecules than for nonpolar molecules, which is consistent with previous studies. However, we found that the lower permeation of charged molecules resulted from the presence of at least two distinct GUV populations; the larger population consisted of impermeable GUVs, and the smaller population consisted of those with a high permeability. The presence of phospholipid vesicles highly permeable to charged and small molecules (<3 nm) was found through the single vesicular measurement. The observed permeability of the GUVs may have played an essential role in the selfreproduction and evolution of primitive cells.

A one-dimensional pyroelectric array detector as a multi-element infrared sensor has been developed by using a new sheet forming method made of PbTiO3 bulk ceramics. This simple fabrication process is cost effective and enables us to control the film thickness accurately, thus decreasing the sensitivity variations that exist in one detector and among different detectors to within 10%. A pyroelectric detector responsivity of 2×104 V/W can be obtained at 10 Hz chopping frequency. A specific detectivity D * of 0.8×108 cm· Hz1/2/W has been achieved. Furthermore, this detector has a sufficient sensitivity for performances at high chopping speeds up to 100 Hz. The time constant of this pyroelectric detector is about 8.6 ms, so the detector has a shorter response time compared with the commercially available conventional pyroelectric detector. The cross talk, which influences the output for the adjacent elements, is less than 10%. By using this high performance pyroelectric array detector, the thermal sources at lower temperatures than environmental conditions can be detected with high sensitivity, as much as the thermal sources at higher temperatures. The output voltage for the detector was gradually decreased as the atmospheric temperature increased.

A one-dimensional pyroelectric array detector for use as a multielement infrared sensor has been developed by using PbTiO3 bulk ceramics fabricated by a sheet-forming method. This one-dimensional infrared sensor consists of 16 elements. A pyroelectric detector responsivity of 3×104 V/W can be obtained at a 10 Hz chopping frequency, and a specific detectivity D * of 1.2×108 cm·Hz1/2/W has been achieved. The time constant of this pyroelectric detector is about 5.2 ms, so the detector has a shorter response time compared with a commercially available conventional pyroelectric detector. The crosstalk, which influences the output for the adjacent elements, is less than 10%. The output voltage for the detector gradually decreased as the atmospheric temperature increased. Pyroelectric detector responsivity increases with decreasing electrode size. By using this high-performance pyroelectric array detector, the thermal sources at lower temperatures than that of the environment can be detected with high sensitivity, as much as in the case of the thermal sources at higher temperatures.

The authors focus on the retina in the human eye and consider retinoic acid to be the most appropriate for use in photoreceptive devices. The authors fabricated retinoic acid–chitosan film by using the layer-by-layer self-assembly process. The photocurrent value of the devices increased from 4·0 to 7·0 mA when used in optimized conditions. One of the best responses of these manually fabricated photoreceptive devices was that the photocurrent was 7 mA and the photocurrent response continued during the longest period to date of 9 h, which is an 81 times longer life time than before. The authors calculated the external quantum efficiency of the photocurrent response for devices with the best performance. The estimated external quantum efficiency of the photocurrent response for the best device was 4·53. In comparison, for one of the gel-type devices, the efficiency was 0·004. The mechanism of the photocurrent response of biophotonic devices seems to be the radical reaction rather than any ionic or charged carrier reaction.