[Construction and stability analysis of finite element model for spinal canal reconstruction with miniplates fixation].

OBJECTIVE: To establish the finite element model of spinal canal reconstruction and internal fixation,analysis influence of spinal canal reconstruction and internal fixation on spinal stability,and verify the effectiveness and reliability of spinal canal reconstruction and internal fixation in spinal canal surgery. METHODS: A 30-year-old male healthy volunteer with a height of 172 cm and weight of 75 kg was selected and his lumbar CT data were collected to establish a finite element model of normal lumbar L3-L5,and the results were compared with in vitro solid results and published finite element analysis results to verify the validity of the model. They were divided into normal group,laminectomy group and spinal canal reconstruction group according to different treatment methods. Under the same boundary fixation and physiological load conditions,six kinds of activities were performed,including forward bending,backward extension,left bending,right bending,left rotation and right rotation,and the changes of range of motion (ROM) of L3-L4,L4-L5 segments and overall maximum ROM of L3-L5 were analyzed under the six conditions. RESULTS: The ROM displacement range of each segment of the constructed L3-L5 finite element model was consistent with the in vitro solid results and previous literature data,which confirms the validity of the model. In L3-L4,ROM of spinal canal reconstruction group was slightly increased than that of normal group during posterior extension(>5% difference),and ROM of other conditions was similar to that of normal group(<5% difference). ROM in laminectomy group was significantly increase than that in normal group and spinal canal reconstruction group under the condition of flexion,extension,left and right rotation. In L4-L5,ROM in spinal canal reconstruction group was similar to that in normal group(<5% difference),while ROM in laminectomy group was significantly higher than that in normal group and spinal canal reconstruction group(>5% difference). In the overall maximum ROM of L3-L5,spinal canal reconstruction group was only slightly higher than normal group under the condition of posterior extension(>5% difference),while laminectomy was significantly higher than normal group and spinal canal reconstruction group under the condition of anterior flexion,posterior extension,left and right rotation(>5% difference). The changes of each segment ROM and overall ROM of L3-L5 showed laminectomy group>spinal canal reconstruction group>normal group. CONCLUSION: Laminectomy could seriously affect biomechanical stability of the spine,but application of spinal canal reconstruction and internal fixation could effectively reduce ROM displacement of the responsible segment of spine and maintain its biomechanical stability.

Biocontrol activity of recombinant aspartic protease from Trichoderma harzianum against pathogenic fungi.

The use of cell wall degrading enzymes of Trichoderma is a promising alternative for improving food storage. The aspartic protease P6281 secreted by the fungus Trichoderma harzianum plays an important role in mycoparasitism on phytopathogenic fungi. In this study, recombinant P6281 (rP6281) expressed in Pichia pastoris showed high activity of 321.8 U/mL. Maximum activity was observed at pH 2.5 and 40 °C, and the enzyme was stable in the pH range of 2.5-6.0. rP6281 significantly inhibited spore germination and growth of plant and animal pathogenic fungi such as Botrytis cinerea, Mucor circinelloides, Aspergillus fumigatus, Aspergillus flavus, Rhizoctonia solani, and Candida albicans. Transmission electron microscopy revealed that rP6281 efficiently damages the cell wall of Botrytis cinerea. In addition, the protease significantly inhibited the development of grey mold that causes rotting of apple, orange, and cucumber, indicating that rP6281 may be developed as an effective anti-mold agent for fruit storage.

The Structure and Enzyme Characteristics of a Recombinant Leucine Aminopeptidase rLap1 from Aspergillus sojae and Its Application in Debittering.

A leucine aminopeptidase Lap1 was cloned from Aspergillus sojae GIM3.30. The truncated Lap1 without a signal peptide was over-expressed in P. pastoris, and the enzymatic characteristics of recombinant Lap1 (rLap1) were tested. The rLap1 was about 36.7 kDa with an optimal pH 8.0 and optimal temperature 50 °C for substrate Leu-p-nitroanilide and it sustained 50 % activity after 1 h incubation at 50 °C. The activity of rLap1 was significantly inhibited by EDTA, whereas Co(2+), Mn(2+), and Ca(2+) ions, but not Zn(2+) ions, restored its activity. rLap1 showed the highest activity against Arg-pNA and then Leu-, Lys-, Met-, and Phe-pNA. The 3D structure of rLap1 showed it had a conserved functional charge/dipole complex and a hydrogen bond network of Zn2-D179-S228-Q177-D229-S158 around its active center. An acidic Asp residue was found at the bottom of the substrate binding pocket, which explains its preference for basic N-terminal amino acid substrates such as Arg and Lys. rLap1 improved the degree of hydrolysis of casein and soy protein hydrolysates and also decreased their bitterness, indicating its potential utility in food production.

Enzymatic characteristics of a recombinant neutral protease I (rNpI) from Aspergillus oryzae expressed in Pichia pastoris.

A truncated neutral protease I (NpI) from Aspergillus oryzae 3.042 was expressed in Pichia pastoris with a high enzyme yield of 43101 U/mL. Its optimum pH was about 8.0, and it was stable in the pH range of 5.0-9.0. Its optimum temperature was about 55 °C and retained >90% activity at 50 °C for 120 min. Recombinant NpI (rNpI) was inhibited by Cu(2+) and EDTA. Eight cleavage sites of rNpI in oxidized insulin B-chain were determined by mass spectrometry, and five of them had high hydrophobic amino acid affinity, which makes it efficient in producing antihypertensive peptide IPP from ß-casein and a potential debittering agent. The high degree of hydrolysis (DH) of rNpI to soybean protein (8.8%) and peanut protein (11.1%) compared to papain and alcalase makes it a good candidate in the processing of oil industry byproducts. The mutagenesis of H(429), H(433), and E(453) in the deduced zinc-binding motif confirmed rNpI as a gluzincin. All of these results show the great potential of rNpI to be used in the protein hydrolysis industry.