Nuts can generally be divided into two types: one is seeds, such as sunflower seeds, pumpkin seeds, peanuts, etc.; the other is tree nuts, such as pistachios, hazelnuts, cashews, walnuts, pine nuts, walnuts, chestnuts, almonds. And the macadamia and pecans that have been very hot in the past two years. These nut foods contain more protein, calcium and a variety of vitamins, which can provide the body with a variety of nutrients needed by the brain and body. Mix Nuts,Walnut Nuts,Almond Nuts,Pistachios Nuts Hangzhou Aiyomi food co.,LTD , https://www.aiyomisnacks.com
Currently, there are two ways to synthesize genes. 1 Whole-genome synthesis: This method is generally used for genes that are small and difficult to obtain. The double-stranded gene can be divided into several single-stranded fragments of oligonucleotides (especially when the synthase is above 100 nucleotides), each fragment is controlled to be 40-60 bases in length, and each pair is adjacently complementary There are ~6 bases overlapping between the fragments. All fragments except the ends of the ends of the gene were phosphorylated in vitro. After the mixed annealing, DNA ligase is added to obtain a larger gene fragment. If a subcloning method is required, the larger fragment of the subclone is finally recombined into the entire gene. When using the method of step-by-step ligation and subcloning, it is convenient to recover the gene fragment in the subcloning. Appropriate cleavage sites should be designed on both sides of the fragment, since each subclone can be identified separately, thus reducing the possibility of sequence errors. 2 enzymatic synthesis: This method is also known as semi-synthesis of genes. The entire chemical synthesis of whole genes, especially larger ones, is expensive, and the use of semi-synthetic methods can reduce costs and thus facilitate widespread use. First, an oligonucleotide fragment having 10 to 14 complementary bases between the ends is synthesized, and after annealing, the overlapping region is used as a primer, and in the presence of four kinds of dNTPs, a large fragment of DNA polymerase I (Klenow enzyme) or The role of transcriptase is to obtain two complete complementary duplexes. In the structure of the synthetic gene, all the signals and DNA sequences required for cloning and expression should be included, and the reading frame of the gene code should also be compatible with the expression system. In addition, since the use of different kinds of organisms or codons is clearly selective, this problem must be considered in gene synthesis and cloning. Choose the appropriate codon for efficient expression.
2. Primers for sequence determination: DNA sequence determination is the most important and finest research technique in molecular biology. The most commonly used method is end termination, which is a sequence determination method that relies on specific DNA primers. The method requires a large amount of template, which requires that the DNA fragment to be tested, especially the fragment with a small copy number, is first cloned into a suitable vector and amplified for sequence determination. Commonly used cloning vectors such as M13, pUC19, PBR322, etc., are commercially available as common sequencing primers.
3. Synthesis of Primers for Introduction of Mutations: Oligonucleotide-directed mutations can produce point mutations, insertions, and deletions in any part of the DNA sequence of interest, thereby altering the structure and function of the gene-encoded protein.
Synthetic nucleic acids can not only be used as a means of medicine, but also have shown promising advances in the treatment of tumors with the discovery of de facto oligonucleotides and their derivatives in the treatment of certain diseases. Oligonucleotides that are protein translation inhibitors are now referred to as antisense RNA or antisense DNA. The principle of action may be as follows: 1 Antisense RNA binds to the target mRNA in vivo to form a double helix, so that the mRNA cannot be a template for the translated protein. 2 Antisense RNA (DNA) binds to DNA. Affect DNA replication. 3 antisense RNA can prevent mRNA from binding to ribosome and reduce protein synthesis efficiency.
Antisense RNA or antisense DNA has been the hotspot of international research topics in recent years. People hope that it will play an important role in anti-virus, especially on AIDS and tumor gene therapy, and contribute to the conquest of these two types of diseases that seriously threaten human health.
In general, a nut is a closed fruit classification of a nutrient-covered woody or leathery hard shell. The skin is hard and contains one or more seeds. It includes two types of tree nuts and fruit seeds, walnuts, chestnuts, pistachios, almonds, etc., melon seeds, which belong to the fruit seed class.
Application of DNA chemical synthesis
With the development of DNA synthesis technology, especially the introduction of automated synthesis technology, people can synthesize DNA fragments of interest in a simple, rapid and efficient manner. At present, DNA synthesis technology has become an indispensable means of molecular biology research, and has played an increasingly important role in various fields such as genetic engineering, clinical diagnosis and treatment, and forensic medicine.
1. Application of DNA synthesis in genetic engineering and molecular biology research
1.1 Synthetic Genes Nucleotide and amino acid sequences of many genes and proteins have been elucidated, and peptide and protein genes with practical application and research value can be synthesized as needed. Synthetic genes such as human growth hormone, interferon, insulin, epidermal growth factor, interleukin II, colony stimulating factor, etc. have been reported, and these genes have been cloned, and most of them have been expressed in prokaryotic and eukaryotic systems. The Shanghai Institute of Biochemistry and other units in China first synthesized the biologically active yeast alanine transfer ribonucleic acid in the world in 19841, contributing to the application of human civilization.
1.2 The cloning and isolation of synthetic probe genes has become an indispensable means of modern molecular biology research. DNA synthesis technology plays an increasingly important role in it. It not only makes the past screening and identification of genes in the past become a routine technique, but also makes the construction of cloning vectors and the connection of cloned genes and vectors easier and more accurate. The structure of the protein can be indirectly derived from the structure of the mRNA. Conversely, if the amino acid sequence of a peptide is known, all possible mRNA sequence codes can also be derived based on the principle of degeneracy of the code. Artificially synthesized oligo DNA fragments of a particular order have been used to screen and identify recombinant plasmids or lambda phage. Experiments have shown that with synthetic oligonucleotide fragments, even a single pair of base mismatches can be distinguished from fully complementary duplexes by stringent conditional hybridization. Therefore, when using the oligonucleotide as a probe, the degeneracy of the password should be adjusted to the maximum limit, which can reduce false positives and increase the accuracy of screening.
1.3 Synthesis of primers 1. Synthesis of PCR primers for gene amplification: PCR technology was developed in the mid-1980s to amplify specific DNA fragments in vitro. The method is easy to operate and can obtain millions of copies of specific DNA sequences in a test tube in a short time. The specificity of the PCR technique depends on the specificity of the binding of the primers used and the template DNA. The use of synthetic primers in PCR reactions.
1.4 Synthetic linkers and connectors
It is often necessary to insert a foreign DNA fragment into certain vector DNA in DNA recombination. If there is no suitable restriction endonuclease site on the vector or foreign DNA, a method of synthesizing a linker and an adaptor can be employed to increase insertion efficiency or to achieve directional cloning. The use of a linker and a linker requires that the insert be blunt-ended. Otherwise, it is first required to be filled with a large fragment of DNA polymerase I or treated with nuclease S1 or Bal 31 to obtain a blunt end before it can be ligated to a linker or linker.
Polylinkers with multiple enzyme cleavage sites are also widely used to construct certain vectors with multiple new cleavage sites. This has been widely used in both the plasmid pUC series and the M 13 mp phage system for sequence analysis. The linker fragment is used to adjust the reading frame of the expression vector for gene expression and function studies.
2The application of synthetic genes in medicine
With the development of science and technology, people's understanding of diseases has gradually deepened from the level of the whole and the organs to the level of cellular molecules. Medical scientists have found that many diseases that seriously endanger human health, such as hereditary diseases, tumors, cardiovascular diseases, etc., can find some changes in the genetic structure, such as the absence of genes, mutations, translocations, or the presence of pathogenic left causes. Using this as evidence can also make corresponding judgments on these diseases. For example, sickle cell anemia is caused by the A→T mutation causing the sixth glutamate of β-globin to become proline, which causes abnormal globin structure and causes changes in red blood cell morphology and affinity for oxygen. By artificially synthesizing 19 nucleotides as probes, it is possible to clearly distinguish between normal, heterozygous and homozygous patients. At present, synthetic DNA probes have been widely used in clinical practice and become an effective diagnostic tool.
2.1 Diagnosis for genetic diseases In the past, only a few genetic diseases can be judged by abnormalities in protein and enzymology. With the development of molecular biology, the diagnosis of genetic diseases has made great progress, and genes have emerged. Diagnostic method. The earliest successful report on the use of genetic diagnosis in medicine was the diagnosis of sickle cell anemia in 1985 by Saiki et al. In addition, for the β-thalassemia mainly composed of mutations, synthetic DNA fragments were used as probes, and satisfactory results were obtained.
2.2 Diagnostics for infectious diseases The traditional diagnostic procedure for infectious diseases is often the detection of turbidity pathogens and their antibodies, which takes a long time and does not achieve the purpose of early diagnosis. Synthetic probes have been widely used in the detection of infectious diseases, especially infectious diseases caused by viral infectivity, especially in combination with PCR methods, the sensitivity of diagnosis can be further improved. At present, hepatitis B virus and HIV have been tested in China. A variety of gene probe diagnostic kits for HIV, rotavirus and herpes diseases.