Polymorphisms of Epstein-Barr virus BHRF1 gene, a homologue of bcl-2

Background and Objective: EBV BamHI fragment H rightward open reading frame 1 (BHRF1), the Epstein-Barr virus (EBV) early gene, is structurally and functionally homologous to the oncogene bcl-2 and may play an important role in the development of EBV-associated tumors. To characterize the polymorphisms of BHRF1 in EBV-associated tumors, we analyzed the sequences of BHRF1 in isolates from nasopharyngeal carcinoma (NPC) and EBV-associated gastric carcinoma (EBVaGC) biopsies as well as throat washing (TW) samples from healthy donors. Methods: BHRF1 DNA sequences were analyzed by polymerase chain reaction (PCR) and sequencing for 39 NPC samples, 40 EBVaGC samples, and 53 EBV-positive TW samples from healthy donors. The variants of BHRF1 gene were classified according to the signature changes. The EBV types 1 and 2 at nuclear antigen (EBNA) 3C locus were determined by PCR. Results: Compared with EBV standard cell line B95-8, all isolates carried a silent mutation at amino acid (AA) 80 (nucleotide 54616 T→C), the AA88 L→V mutation was found in most isolates, and the AA79 V→L mutation in a few isolates. Other mutations were sporadically distributed. Based on the mutations at AA88 and AA79, 3 distinct variants of BHRF1 genes, designated as 79V88V, 79L88L, and 79V88L, were identified. The 79V88V was the most common variant. The distribution of the BHRF1 variants among the NPC, EBVaGC, and TW samples was not significant. The corresponding regions of bcl-2 homologues were conserved in all isolates except for 3 samples. The distribution of BHRF1 variants in type 1 and type 2 strains was significant different (P < 0.001, contingency coefficient was 0.554). Conclusions: The 79V88V is the dominant variant in NPC, EBVaGC, and TW samples from healthy donors and preferential linkages between BHRF1 and EBNA3C variants exist. Conserved BHRF1 in Bcl-2 homologous domains is helpful to remain the important role of BHRF1.

Review of improved spectral response of ultraviolet photodetectors by surface plasmon

Ultraviolet(UV) photodetectors based on wide band gap semiconductor have attracted much attention for their small volume, low working voltage, long lifetime, good chemical and thermal stability. Up to now, many researches have been done on the semiconductors based UV detectors and some kinds of detectors have been made, such as metal–semiconductor–metal(MSM), Schottky, and PIN-type detectors. However, the sensitivity values of those detectors are still far from the expectation. Recent years, surface plasmon(SP) has been considered to be an effective way to enhance the sensitivity of semiconductor based UV photodetector. When the light is matched with the resonance frequency of surface plasmon, the localized field enhancement or scattering effect will happen and thus the spectral response will be enhanced.Here, we present an overview of surface plasmon enhancing the performance of UV detectors, including the GaN, ZnO,and other wide band gap semiconductor UV detectors. Both fundamental and experimental achievements are contained in this review.

Direct observation of localized surface plasmon field enhancement by Kelvin probe force microscopy

A surface plasmon(SP)is a fundamental excitation state that exists in metal nanostructures.Over the past several years,the performance of optoelectronic devices has been improved greatly via the SP enhancement effect.In our previous work,the responsivity of GaN ultraviolet detectors was increased by over 30 times when using Ag nanoparticles.However,the physics of the SP enhancement effect has not been established definitely because of the lack of experimental evidence.To reveal the physical origin of this enhancement,Kelvin probe force microscopy(KPFM)was used to observe the SP-induced surface potential reduction in the vicinity of Ag nanoparticles on a GaN epilayer.Under ultraviolet illumination,the localized field enhancement induced by the SP forces the photogenerated electrons to drift close to the Ag nanoparticles,leading to a reduction of the surface potential around the Ag nanoparticles on the GaN epilayer.For an isolated Ag nanoparticle with a diameter of~200 nm,the distribution of the SP localized field is located within 60 nm of the boundary of the Ag nanoparticle.For a dimer of Ag nanoparticles,the localized field enhancement between the nanoparticles was the strongest.The results presented here provide direct experimental proof of the localized field enhancement.These results not only explain the high performance of GaN detectors observed with the use of Ag nanoparticles but also reveal the physical mechanism of SP enhancement in optoelectronic devices,which will help us further understand and improve the performance of SP-based optoelectronic devices in the future.