Rationalizing the Structural Variability of the Exocyclic Amino Groups in Nucleobases and Their Metal Complexes: Cytosine and Adenine

2014 ◽  
Vol 20 (31) ◽  
pp. 9494-9499 ◽  
Author(s):  
Célia Fonseca Guerra ◽  
Pablo J. Sanz Miguel ◽  
Andrea Cebollada ◽  
F. Matthias Bickelhaupt ◽  
Bernhard Lippert
Keyword(s):  
Metal Complexes ◽  
Amino Groups ◽  
Structural Variability

Crystal structure of dichlorobis(1-methylcytosine)cadmium(II)

1979 ◽  
Vol 57 (11) ◽  
pp. 1372-1376 ◽  
Author(s):  
Carole Gagnon ◽  
André L. Beauchamp ◽  
Duc Tranqui
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonds ◽  
Metal Complexes ◽  
Carbonyl Group ◽  
Steric Hindrance ◽  
Amino Group ◽  
Amino Groups ◽  
R Factor ◽  
The Difference ◽  
Intramolecular Hydrogen

Crystals of CdCl2(1-methylcytosine)2 belong to space group Cc, with a = 10.571(7), b = 24.35(2), c = 7.097(3) Å, β = 57.33(4)°, and Z = 4. The structure was refined over 1988 independent reflections to an R factor of 0.026. The structure consists of monomeric molecules in which cadmium has a (4 + 2)-coordination. Four strong bonds, two Cd—Cl (2.497, 2.485 Å) and two Cd—N(3) (2.281, 2.296 Å), define an approximate tetrahedron around the metal. Two carbonyl oxygens take part in weak Cd—O bonding interactions (2.677, 2.780 Å). The amino groups form only very weak intramolecular hydrogen bonds with chlorine and the difference >30° between angles Cd—N(3)—C(4) and Cd—N(3)—C(2) is ascribed to Cd—O bonding. Similar effects for other metal complexes are discussed in terms of steric hindrance of the amino group and bonding of the carbonyl group.

Aldehyde gold clusters for molecular labeling

1995 ◽  
Vol 53 ◽  
pp. 858-859
Author(s):  
James F. Hainfeld ◽  
Frederic R. Furuya
Keyword(s):  
Covalent Bond ◽  
Aldehyde Group ◽  
Gold Clusters ◽  
Side Reactions ◽  
Amino Groups ◽  
Sodium Cyanoborohydride ◽  
Schiff’S Base ◽  
Protein Molecules ◽  
Hydroxysuccinimide Esters ◽  
Primary Amino

Glutaraldehyde is a useful tissue and molecular fixing reagents. The aldehyde moiety reacts mainly with primary amino groups to form a Schiff's base, which is reversible but reasonably stable at pH 7; a stable covalent bond may be formed by reduction with, e.g., sodium cyanoborohydride (Fig. 1). The bifunctional glutaraldehyde, (CHO-(CH2)3-CHO), successfully stabilizes protein molecules due to generally plentiful amines on their surface; bovine serum albumin has 60; 59 lysines + 1 α-amino. With some enzymes, catalytic activity after fixing is preserved; with respect to antigens, glutaraldehyde treatment can compromise their recognition by antibodies in some cases. Complicating the chemistry somewhat are the reported side reactions, where glutaraldehyde reacts with other amino acid side chains, cysteine, histidine, and tyrosine. It has also been reported that glutaraldehyde can polymerize in aqueous solution. Newer crosslinkers have been found that are more specific for the amino group, such as the N-hydroxysuccinimide esters, and are commonly preferred for forming conjugates. However, most of these linkers hydrolyze in solution, so that the activity is lost over several hours, whereas the aldehyde group is stable in solution, and may have an advantage of overall efficiency.

Mechanochemical changes on cyclometalated Ir(iii) acyclic carbene complexes – design and tuning of luminescent mechanochromic transition metal complexes

2020 ◽  
Vol 7 (3) ◽  
pp. 786-794 ◽  
Author(s):  
Jingqi Han ◽  
Kin-Man Tang ◽  
Shun-Cheung Cheng ◽  
Chi-On Ng ◽  
Yuen-Kiu Chun ◽  
...  
Keyword(s):  
Transition Metal ◽  
Metal Complexes ◽  
Transition Metal Complexes ◽  
Carbene Complexes ◽  
New Class

A new class of luminescent cyclometalated Ir(iii) complexes with readily tunable mechanochromic properties derived from the mechanically induced trans-to-cis isomerization have been developed.

The Action of Thrombin on Modified Fibrinogen

1983 ◽  
Vol 49 (03) ◽  
pp. 208-213
Author(s):  
A J Osbahr
Keyword(s):  
Physical Properties ◽  
Negative Charge ◽  
Lysine Residue ◽  
Fibrinopeptide A ◽  
Amino Groups ◽  
Lysine Residues ◽  
Citraconic Anhydride

SummaryThe modification of canine fibrinogen with citraconic anhydride modified the ε-amino groups of the fibrinogen and at the same time generated additional negative charges into the protein. The addition of thrombin to the modified fibrinogen did not induce polymerization; however, the fibrinopeptide was released at a faster rate than from the unmodified fibrinogen. The physical properties of the citraconylated fibrinogen were markedly altered by the modification of 50-60 lysine residues in one hour. A modified fibrinopeptide-A was released by thrombin from the modified fibrinogen and was electrophoretically more anionic than the unmodified fibrinopeptide-A. Edman analysis confirmed the modification of the lysine residue present in the peptide. The rate of removal of citraconylated fibrinopeptide-A from modified fibrinogen by thrombin was 30 to 40 percent greater than the cleavage of unmodified fibrinopeptide-A from unmodified fibrinogen. However, the modification of 60 or more lysine residues in the fibrinogen produced a decrease in the rate of cleavage of citraconylated fibrinopeptide-A. The results suggest that additional negative charge in the vicinity of the attachment of fibrinopeptide-A to canine fibrinogen aids in the removal of the peptide by thrombin.

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