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Dehydration synthesis reactions _____, ..
Riboflavin is an essential vitamin for cellular metabolism, and the riboflavin carrier protein (RCP) is highly upregulated in metabolically active cells [,]. Thus, flavin mononucleotide (FMN), an endogenous RCP ligand, was used as a small molecule targeting ligand for metabolically active cancer or endothelial cells. Kiessling and co-workers synthesized FMN-coated ultrasmall superparamagnetic iron oxide nanoparticles (FLUSPIO) as MRI/optical dual probes for cancer detection . USPIO was coated with FMN through the phosphate groups of FMN, and guanosine monophosphate was added to stabilize the colloid. The hydrodynamic radius of FLUSPIO was 97 ± 3 nm, and an intense fluorescence emission band was observed at 530 nm due to FMN. cellular uptake of FLUSPIO was investigated by MRI (3T), TEM, and fluorescence microscopy of PC3 cells and HUVEC cells. Both PC3 cells and HUVEC cells showed a significantly higher R2 relaxation rate after 1 h incubation with FLUSPIO than with nontargeted USPIO. Such an uptake was considerably reduced by competitive blocking of RCP with free FMN. A strong green fluorescence in the cells was observed after FLUSPIO incubation. The perinuclear fluorescence signal suggested endosomal localization of the nanoparticles, consistent with TEM results, suggesting that FMN could serve as a versatile building block for generating tumor-targeted imaging and therapeutic modalities.
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Ellington . used this bioconjugation method to conjugate an anti-EGFR aptamer onto GNPs to demonstrate the targeting specificity of a newly identified aptamer . As described above, they coated GNPs with thiol-modified capture ONTs that hybridized to an extended anti-EGFR aptamer to generate anti-EGFR aptamer-conjugated GNPs. Jon . utilized the hybridization method to conjugate an anti-PSMA-aptamer to iron oxide nanoparticle surfaces . In their study, CG-rich duplexes were constructed at the ends of the aptamers to achieve multiple Dox-binding on the nanoparticles. They immobilized amine-functionalized capture ONTs (5'NH2-A10-(TCG)7-3') on the surfaces of the carboxyl-modified iron oxide nanoparticles. Magnet purification yielded the capture ONT-coated iron oxide nanoparticles. A (CGA)7-extended anti-PSMA-aptamer was synthesized by transcription, and the aptamers were added to the ONT-coated nanoparticles to produce Apt--TCL-SPIONs. Thermal gravimetric analysis (TGA) indicated that PSMA aptamers (28,451 Da) hybridized to approximately 33% of the ONTs (9,708 Da) conjugated to the nanoparticles. aptamers capture ONTshe surface of nanoparticles via staining in larger samples (106 cells).ons [nitude highenn
for the synthesis of the pyrimidine nucleotides
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Histidine is special in that its biosynthesis is inherently linked to thepathways of nucleotide formation. Histidine residues are often found in enzymeactive sites, where the chemistry of the imidazole ring of histidine makes it anucleophile and a good acid/base catalyzer. We now know that RNA can havecatalytic properties, and there has been speculation that life was originallyRNA-based. Perhaps the transition to protein catalysis from RNA catalysisoccurred at the origin of histidine biosynthesis.
GNPs can couple to thiol-modified functional moieties without the need for additional functional groups. Because Au is highly reactive toward thiol groups, forming a strong Au-S bond, a variety of thiol-functionalized biomolecules may be conjugated to GNP surfaces in a straightforward manner. Oligonucleotide-based molecules, such as siRNA, are usually chemically synthesized to contain sulfhydryl groups that can then be conjugated to GNPs. When Li . synthesized the folate-receptor targeted hollow gold nanospheres carrying siRNA, they conjugated thiol-modified siRNA duplexes directly to the surfaces of HAuNS .
Quick revisions | Biochemistry for Medics – Lecture Notes
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Plants and bacteria synthesize all 20 common amino acids. Mammals cansynthesize about half; the others are required in the diet (essential aminoacids). Among the nonessential amino acids, glutamate is formed byreductive amination of α-ketoglutarate and serves as the precursor of glutamine,proline, and arginine. Alanine and aspartate (and thus asparagine) are formedfrom pyruvate and oxaloacetate, respectively, by transamination. The carbonchain of serine is derived from 3-phosphoglycerate. Serine is a precursor ofglycine; the β-carbon atom of serine is transferred to tetrahydrofolate. Inmicroorganisms, cysteine is produced from serine and from sulfide produced bythe reduction of environmental sulfate. Mammals produce cysteine from methionineand serine by a series of reactions requiring S-adenosylmethionine andcystathionine. Among the essential amino acids, the aromatic amino acids(phenylalanine, tyrosine, and tryptophan) form by a pathway in which chorismateoccupies a key branch point. Phosphoribosyl pyrophosphate is a precursor oftryptophan and histidine. The pathway to histidine is interconnected with thepurine synthetic pathway. Tyrosine can also be formed by hydroxylation ofphenylalanine (and thus is considered conditionally essential). The pathways forthe other essential amino acids are complex. The amino acid biosyntheticpathways are subject to allosteric end-product inhibition; the regulatory enzymeis usually the first in the sequence. Regulation of the various syntheticpathways is coordinated.
FIGURE 159 Interlocking regulatory mechanisms in the biosynthesisof several amino acids derived from aspartate in E. coli. Threeenzymes (A, B, C) have either two or three isozyme forms, indicatedby numerical subscripts. In each case, one isozyme (A2, B1, and C2)has no allosteric regulation; these isozymes are regulated by changesin the amount synthesized. Synthesis of isozymes A2 andB1 is repressed when methionine levels are high, and synthesis ofisozyme C2 is repressed when isoleucine levels are high. Enzyme Ais aspartokinase; B, homoserine dehydrogenase; C, threonine dehydratase.
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Biology answers – Easy Peasy All-in-One High School
FIGURE 151 Overview of amino acid biosynthesis. The carbon skeletonprecursors derive from three sources: glycolysis (pink), the citric acid cycle(blue), and the pentose phosphate pathway (purple).
How To Maximize Performance And Increase Muscle …
Histidine is derived from three precursors (Fig. 158): PRPP contributesfive carbons, the purine ring of ATP contributes a nitrogen and a carbon, andglutamine supplies the second ring nitrogen. The key steps are condensation ofATP and PRPP, in which N-1 of the purine ring is linked to the activated C-1 ofthe ribose of PRPP (step 1); purine ring opening that ultimately leaves N-1 andC-2 of adenine linked to the ribose (step 3); and formation of the imidazolering, a reaction in which glutamine donates a nitrogen (step 5). The use of ATPas a metabolite rather than a high-energy cofactor is unusual but not wasteful,because it dovetails with the purine biosynthetic pathway. The remnant of ATPthat is released after the transfer of N-1 and C-2 is5-aminoimidazole-4-carboxamide ribonucleotide (AICAR), an intermediate of purinebiosynthesis that is rapidly recycled to ATP.
IJMS | April 2016 - Browse Articles
FIGURE 158 Biosynthesis of histidine in bacteria and plants. Atomsderived from PRPP and ATP are shaded red and blue, respectively. Two of thehistidine nitrogens are derived from glutamine and glutamate (green). Note thatthe derivative of ATP remaining after step 5 (AICAR) is an intermediate inpurine biosynthesis, so ATP is rapidly regenerated.
Metals and Life Chapter 9 - Royal Society of Chemistry
Nitrogen ranks behind only carbon, hydrogen, and oxygen in itscontribution to the mass of living systems. Most of this nitrogen is bound up inamino acids and nucleotides. The biosynthetic pathways for amino acids shareseveral key intermediates with those of nucleotides which will be discussed inthe next chapter. Certain amino acids or parts of amino acids are incorporatedinto the structure of purines and pyrimidines, and in one case part of a purinering is incorporated into an amino acid (histidine). The two sets of pathwaysalso share much common chemistry, in particular a preponderance of reactionsinvolving the transfer of nitrogen or onecarbon groups.
All amino acids are derived from intermediates in glycolysis, the citric acidcycle, or the pentose phosphate pathway (Fig. 151). Nitrogen enters thesepathways by way of glutamate and glutamine. Some pathways are simple, others arenot. Ten of the amino acids are just one or several steps removed from thecommon metabolite from which they are derived. The biosynthetic pathways forothers, such as the aromatic amino acids, are more complex.
A useful way to organize these biosynthetic pathways is to group them into sixfamilies corresponding to their metabolic precursors (Table 151), and we usethis approach to structure the detailed descriptions that follow.
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