Bt杀虫晶体蛋白的土壤残留及其对土壤磷酸酶活性的影响

研究表明以不同形式导入土壤中的杀虫晶体蛋白在土壤中的残留特性及其对土壤磷酸酶活性的影响有所不同。以Bt菌体向土壤导入杀虫晶体蛋白的试验表明 :随着培养时间的延长 ,土壤中杀虫晶体蛋白含量逐渐增加 ,到 1 5d时达到一个峰值 ,而后下降 ,在培养 30d时 ,杀虫晶体蛋白含量基本与初始含量相同。以不同Bt棉组织添加土壤的试验表明 :随着培养时间的延长 ,土壤中的杀虫晶体蛋白含量降低 ,在培养初期下降的速度较快 ,随后下降的速度较慢 ,在培养的中后期基本稳定 ,在培养 5 6d时 ,杀虫晶体蛋白含量为初始值的 4 4 7%(ZK)和 5 6 1 %(GK)。不同Bt棉的盆栽试验表明 :在整个生育期内 ,Bt棉花种植后根际土壤中杀虫晶体蛋白含量均明显比非Bt棉高。Bt菌体和Bt棉组织处理的土壤磷酸酶活性均呈现出比对照高的趋势 ,而在Bt棉种植过程中Bt棉根际土壤的磷酸酶活性则呈现出比非Bt棉低的趋势。无论以何种方式向土壤中导入杀虫晶体蛋白 ,土壤磷酸酶活性在不同杀虫晶体蛋白浓度处理间的差异显著。

Molecular modeling of Bt Cry1Ac (DI–DII)–ASAL (Allium sativum lectin)–fusion protein and its interaction with aminopeptidase N (APN) receptor of Manduca sexta

Genetic engineering of Bacillus thuringiensis (Bt) Cry proteins has resulted in the synthesis of various novel toxin proteins with enhanced insecticidal activity and specificity towards different insect pests. In this study, a fusion protein consisting of the DI–DII domains of Cry1Ac and garlic lectin (ASAL) has been designed in silico by replacing the DIII domain of Cry1Ac with ASAL. The binding interface between the DI–DII domains of Cry1Ac and lectin has been identified using protein–protein docking studies. Free energy of binding calculations and interaction profiles between the Cry1Ac and lectin domains confirmed the stability of fusion protein. A total of 18 hydrogen bonds was observed in the DI–DII–lectin fusion protein compared to 11 hydrogen bonds in the Cry1Ac (DI–DII–DIII) protein. Molecular mechanics/Poisson–Boltzmann (generalized-Born) surface area [MM/PB (GB) SA] methods were used for predicting free energy of interactions of the fusion proteins. Protein–protein docking studies based on the number of hydrogen bonds, hydrophobic interactions, aromatic–aromatic, aromatic–sulphur, cation–pi interactions and binding energy of Cry1Ac/fusion proteins with the aminopeptidase N (APN) of Manduca sexta rationalised the higher binding affinity of the fusion protein with the APN receptor compared to that of the Cry1Ac–APN complex, as predicted by ZDOCK, Rosetta and ClusPro analysis. The molecular binding interface between the fusion protein and the APN receptor is well packed, analogously to that of the Cry1Ac–APN complex. These findings offer scope for the design and development of customized fusion molecules for improved pest management in crop plants.

Estimation of BT Interference in OFDM Sub Carriers with Training Signals

While wireless LAN (WLAN) is very popular now a days, its performance deteriorates in the presence of other signals like Bluetooth (BT) signal that operate in the same band as WLAN. Present interference mitigation techniques in WLAN due to BT cancel interference in WLAN sub carrier where BT has hopped but do not cancel interference in the adjacent sub carriers. In this paper BT interference signal in all the OFDM sub carriers is estimated. That is, leakage of BT in other sub carriers including the sub carriers in which it has hopped is also measured. BT signals are estimated using the training signals of OFDM system. Simulation results in AWGN noise show that proposed algorithm agrees closely with theoretical results.

Estimation of BT interference and equivalent channel tap in multipath fading channel

One of the major sources of interference for WLANs operating in 2.4GHz unlicensed ISM is Bluetooth (BT). Though OFDM based WLAN's have features like strong immunity to multipath channel effects, its performance detoriates severely whenever there is BT operating nearby. Even for high SIR (Signal to Interference Ratio), performance does not improve much because WLAN is not able to estimate correctly all its channel parameters in presence of BT interference. So, in this paper, the authors propose an algorithm for estimating BT interference and equivalent channel filter tap values.

BT-benzo-29 inhibits bacterial cell proliferation by perturbing FtsZ assembly

We have identified a potent antibacterial agent N-(4-sec-butylphenyl)-2-(thiophen-2-yl)-1H-benzod]imidazole-4-carboxa mide (BT-benzo-29) from a library of benzimidazole derivatives that stalled bacterial division by inhibiting FtsZ assembly. A short (5 min) exposure of BT-benzo-29 disassembled the cytokinetic Z-ring in Bacillus subtilis cells without affecting the cell length and nucleoids. BT-benzo-29 also perturbed the localization of early and late division proteins such as FtsA, ZapA and SepF at the mid-cell. Further, BT-benzo-29 bound to FtsZ with a dissociation constant of 24 +/- 3 m and inhibited the assembly and GTPase activity of purified FtsZ. A docking analysis suggested that BT-benzo-29 may bind to FtsZ at the C-terminal domain near the T7 loop. BT-benzo-29 displayed significantly weaker inhibitory effects on the assembly and GTPase activity of two mutants (L272A and V275A) of FtsZ supporting the prediction of the docking analysis. Further, BT-benzo-29 did not appear to inhibit DNA duplication and nucleoid segregation and it did not perturb the membrane potential of B. subtilis cells. The results suggested that BT-benzo-29 exerts its potent antibacterial activity by inhibiting FtsZ assembly. Interestingly, BT-benzo-29 did not affect the membrane integrity of mammalian red blood cells. BT-benzo-29 bound to tubulin with a much weaker affinity than FtsZ and exerted significantly weaker effects on mammalian cells than on the bacterial cells indicating that the compound may have a strong antibacterial potential.