How to choose an appropriate design type to arrange research factors and their levels is an important issue in scientific research. Choosing an appropriate design type is directly related to the accuracy, scientificness and credibility of a research result. When facing a practical issue, how can researchers choose the most appropriate experimental design type to arrange an experiment based on the research objective and the practical situation? This article mainly introduces the related contents of the design of one factor with two levels and the design of one factor with k (k≥3) levels by analyzing some examples.

Two-factor designs are very commonly used in scientific research. If the two factors have interactions, research designs like the factorial design and the orthogonal design can be adopted; however, these designs usually require many experiments. If the two factors have no interaction or the interaction is not statistically significant on result in theory and in specialty, and the measuring error of experimental data under a certain condition (usually one of the experimental conditions that are formed by the complete combination of the levels of the two factors) is allowed in specialty, researchers can use random block design without repeated experiments, balanced incomplete random block design without repeated experiments, single factor design with a repeatedly measured factor, two-factor design without repeated experiments and two-factor nested design. This article introduces the last two design types by examples.

Objective To investigate the serum levels of semaphorin 3E(Sema3E)in patients with intracranial aneurysms,revealing the correlation between Sema3E and 1-month poor prognosis after interventional embolization.Methods This study was a prospective single-center cohort study,recruiting 102 consecutive patients with intracranial aneurysms who underwent interventional surgery from June 2020 to January 2022 in our hospital.Among them,11 patients were excluded.Clinical and radiological profiles were collected.Peripheral blood was collected after admission,and serum Sema3E levels were determined by enzyme-linked immunosorbent assay.All the aneurysms were treated with endovascular coil embolization or stent-assisted coil embolization.The primary outcome was evaluated with the Glasgow Outcome Scale(GOS)1 month after interventional therapy.The favorable outcome was defined as a GOS score of 4-5,and a poor outcome was defined as a GOS score of 1-3(severe disability,vegetative state,or death).Univariate and multivariate logistic regression analyses were used to identify potential prognostic factors after interventional therapy.Results The average age of 91 patients with intracranial aneurysm was 59.9±11.0 years old,including 70 cases(76.9%)with favorable prognosis and 21 cases(23.1%)with poor prognosis.The mean preoperative Glasgow Coma Scale(GCS)score of the poor prognosis group(9.4±4.5)was significantly lower than that of the favorable prognosis group(13.3±2.5;P<0.001).In the poor prognosis group,the Hunt-Hess grade(3.6±0.6 vs.2.0±1.3,P<0.001)and the serum Sema3E levels[(6.21±1.58)μg/L vs.(4.38±1.77)μg/L,P<0.001]were significantly higher than those in the favorable prognosis group.Logistic regression analysis showed the Hunt-Hess grade(OR =7.150,P =0.003),stent-assisted coil embolization(OR =15.777,P =0.010),and the serum Sema3E level(OR =1.756,P =0.027)were independent prognostic factors for intracranial aneurysms after interventional therapy.Conclusions The serum Sema3E level is closely correlated with the severity of intracranial aneurysms.The serum Sema3E level is a prognostic factor for interventional treatment,which can be used as a biomarker for predicting poor outcomes.

Uridine-cytidine kinase, an important catalyst in the compensation pathway of nucleotide metabolism, can catalyze the phosphorylation reaction of cytidine to 5'-cytidine monophosphate (CMP), but the reaction needs NTP as the phosphate donor. To increase the production efficiency of CMP, uridine-cytidine kinase gene from Thermus thermophilus HB8 and polyphosphate kinase gene from Rhodobacter sphaeroides were cloned and expressed in Escherichia coli BL21(DE3). Uridine-cytidine kinase was used for the generation of CMP from cytidine and ATP, and polyphosphate kinase was used for the regeneration of ATP. Then, the D403 metal chelate resin was used to adsorb Ni²⁺ to form an immobilized carrier, and the immobilized carrier was specifically combined with the recombinant enzymes to form the immobilized enzymes. Finally, single-factor optimization experiment was carried out to determine the reaction conditions of the immobilized enzyme. At 30 °C and pH 8.0, 60 mmol/L cytidine and 0.5 mmol/L ATP were used as substrates to achieve 5 batches of high-efficiency continuous catalytic reaction, and the average molar yield of CMP reached 91.2%. The above method has the advantages of low reaction cost, high product yield and high enzyme utilization rate, and has good applied value for industrial production.
Cytidine Monophosphate ; metabolism ; Escherichia coli ; genetics ; Industrial Microbiology ; methods ; Phosphotransferases (Phosphate Group Acceptor) ; metabolism ; Uridine Kinase